Set Up a Saltwater Aquarium

How to Cycle Your Saltwater Tank

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  1. Avatar Lakshitha says:

    Hi! I’m from a tropical country and I brought a few pieces of uncured live rock lying on the beach. An hour later, I put all of them in a bucket of fresh water. (didn’t have access to salt water at that time) About 12 hours later, I put them in a small tank .(any bad effects from this???) with some dry rock also. but by mistake, I added normal tap water without any dechlorinator in it.(what are it’s bad effects???) then I put a small power head in the tank for oxygenation. No protein skimmer, substrate, filter, heater or lights.(is it OK?) recently, I added some fish food regularly to raise ammonia levels. Now, it is almost 5 weeks since I started.(why aren’t there any good physical changes yet?)I haven’t done any water changes or additions.(is it OK?) The rocks stank at first and had quite a lit of e red, white and green growth, (could those be coralline algae?) but now, there is so little growth (why?)that can be seen and some parts of some rocks turned pure white.(why, again?) And there had appeared a greenish white spot and several white spots that are like solidified wax poured over the rocks.(can those be the beginning of corals or some nice stuff?) Also there are some fluffy cotton-like white things grown over few rocks and is spreading slowly.(what can those be?) and a bit of light brownish growth too, could be diatom bloom.(reason for that???) Also, some rock started to turn a little red all over from being white, a few days after introducing to the tank.(reason for that?) The problem is, although I want to make this successful VERY badly, I don’t have any hydrometers or any indicators to measure the salinity, ammonia, nitrate, nitrite, etc. So, of course I’m struck in the middle right now. I’m still a kid so I couldn’t have access to them nor are there any person or place which can give me the required material or information. I know that I should’ve posted this earlier but I couldn’t find a reliable information source, until now. I also couldn’t find sea salt and had to use table salt.(what are it’s bad effects???)So, I desperately need your help ASAP. Please reply soon.(a very descriptive answer and a point out at what I’m doing wrong and right would be most helpful.) Also, how can I right my mistakes about the salt and water and can I add fish or corals yet? Can corals grow of their own accord without me adding it to the tank? (I want to add the rocks after cycling to a 15 gallon tank which had been used as a goldfish aquarium previously) Will there be enough space? How can I improve the present condition of my tank? Make corals grow faster? How can I seed dry rock? Can I add cured diy live rock to the same tank to become actual live rock or should I start in a new tank? etc… etc… And, thank you in advance for all your highly appreciative help.

  2. Avatar Jason says:

    First time with a SW tank, 55 gal, started the cycle about 6 days ago. I have life rock and live sand. I’ve been adding a few flakes every day to get the cycle going. Today ammonia is at 0.25, N02 @ .25 and N03 @ 5. However there is a horrible smell coming from the tank. I am running 2 power heads and a heater. Please help me get rid of this smell.

  3. Avatar David head says:

    Hi that 12g. Nano cube has glass anemone what so I do to get rid of them without replacing the live rock causing another cycle

    1. Avatar Jeff Kurtz says:

      Hmm, there are all kinds of methods and techniques for treating Aiptasia anemones–for example injecting specimens with calcium hydroxide, boiling water, vinegar, lemon juice, or various proprietary products; or introducing some sort of biological control, such as peppermint shrimp (Lysmata wurdemanni), certain butterflyfish (e.g., Chelmon rostratus), or Berghia nudibranchs. However, not all methods are appropriate for all systems/livestock assemblages, and results for each method tend to vary widely.

  4. Avatar David head says:

    Hi Jeff I’m David and I am buying a 12g nano cube dx tank. It has has been established for 3 years. My question is it’s a 4 hr drive from where I am buying it and was wondering if I have to get it to cycle again after the move or just re add saltwater to it. What do you suggest. I hope it does not have to cycle again. Thanks love your site and all the great advice you have given to other ppl.

    1. Avatar Jeff Kurtz says:

      Thanks for your kind words, David! If it’s possible to avoid subjecting the live rock to significant changes in water conditions during the move, you may be able to keep much of the biofilter intact. Nonetheless, I would advise mixing up plenty of clean (and heated/aerated) salt water ahead of the move. That way, if the cycle does get disrupted and you experience a spike in ammonia or nitrite, you’re already prepared to perform major water changes.

  5. Avatar Holly says:

    Hi I just started up a 75liter red sea max nano tank started with live sand and live rock I tested my water on the 2nd day with fairly ridiculous reading please help! The ph: 8.0 ammonia:12.5ppm nitrite:0 nitrate:well above 160ppm

    1. Avatar Jeff Kurtz says:

      Hi Holly! Your ammonia and nitrate readings certainly are outrageously high, which makes me question their accuracy. What are you using to test these levels? Have you been adding anything to the water at all? Was the live rock cured before it was added to the tank? Also, is there any chance your source water is of questionable quality? Any additional information you can provide might help us zero in on the cause here.

      1. Avatar Holly says:

        I wrote my ammonia wrong it’s .125

        1. Avatar Jeff Kurtz says:

          Ah, that makes more sense. Still wondering about that sky-high nitrate reading though. Have you measured any nitrite at all throughout the process thus far?

          1. Avatar Holly says:

            The first day the nitrite was pretty steep

        2. Avatar Jeff Kurtz says:

          At this point, you’ll just need to let the process play out until you get no measurable ammonia or nitrite. Of course, even at that, you’ll need to do a major water change to bring the nitrate level way down before it will be safe to stock the system.

  6. Avatar Mason says:

    Hi, what a useful website. I have a couple of questions and hope you to help me out.
    I have a 30G tank just running its cycled about a week, with 8 lbs of live rocks.
    1) The staff from LFS who recommend me to get 30lbs or at least 15lbs for my tank. If it is true, can i add more rocks right now?
    2) It is necessary to run a sump during the cycled period?
    3)I made of mistake by buying 10 nails to speed up the cycled period, and now i think they are all died. Should i take out or leave them in the tank?
    Thank you!

    1. Avatar Jeff Kurtz says:

      Thanks for your kind words, Mason! I agree with the staff at your LFS that more live rock is in order here. The usual recommendation is somewhere between 1 and 1.5 pounds of live rock per gallon of aquarium volume, so a total of 30 pounds would be just about right for your tank (though that’s an admittedly rough estimate given that different rocks of the same size can vary dramatically in weight depending on their porosity). And yes, you can add those rocks right now since the system is still cycling.

      As far as a sump is concerned, it’s not absolutely necessary to run one during the cycling period, but keep in mind that a sump will affect the system’s overall water volume, circulation, and gas exchange for the better, so my preference is to use one right from the start.

      With respect to the dead snails, I’d be inclined to remove them. so you don’t get an overwhelming ammonia spike.

      1. Avatar Mason says:

        Hi, the tank is on the 12th day of cycle, ammonia: 0.25, nitrite: 0.0, nitrate: 30 and no algal blooms. At this stage, the ammonia level is supposed to be high and a lot of algae? Any suggestion? Can i put a fish in the tank? Thank you.

        1. Avatar Jeff Kurtz says:

          You definitely don’t want to add any livestock while you’re still measuring ammonia or nitrite. Both of those levels must be at zero before it’s safe to begin stocking. Some measurable nitrate is okay, but you’ll want to bring it down well below the current level before adding livestock.

  7. Avatar Evan Newsome says:

    Hey Jeff Kurtz, I was hoping you could help? I have a 36 gallon tank. Still trying to go through cycle,I had made mistakes early on, and did a fish in cycle.I grew up doing it that way not knowing as an adult there was another way.I digress, I had live rock in first then 4 fish. Its been over a month. i added bio start up earlier on as well, hoping to speed process and achieve decent levels of ammonia etc.

    My issue is my ammonia is at 0, nitrites and nitrates are peaking on my levels chart,but its been like that for over a week now. ive tried to vaccum as much old food as i can find and cut back feedings. only my live rock has brown thick tough algea. What can i do to get this cycle finished and the nitrites down?

    1. Avatar Jeff Kurtz says:

      Hi Evan! It sounds like you’re getting there with your ammonia at 0, though it could still take a few weeks for the cycle to get fully established and your nitrite level to drop. It’s not unusual for the whole process to take upwards of six weeks or more. In the meantime, continue to provide good, stable water conditions, minimal feeding, robust water movement, etc. To help the process along you might also consider adding some “seeded” rock, substrate, or filter media from an established tank to your system if you can source it close by.

      1. Avatar Evan says:

        Thanks for the help jeff. Still have peaked levels of nitrite and nitrate like at the extremes on my chart. Ive been doing daily to frequent water change as well as a few snails to assist with algea build up

        1. Avatar Jeff Kurtz says:

          Hmm, I wonder if you’re getting inaccurate nitrite and nitrate readings for some reason. With those levels at the extremes, I wouldn’t expect snails to survive (or fish for that matter). Any chance you have outdated kits?

          1. Avatar Evan says:

            Hey jeff, love the help! Yea i took a sample to the LFS and the nitrites are peaked but nitrates are only halfway. Perhaps my nitrate reader is off. Im guessing its just a waiting game. My ph is in the 7’s so i was told to stop doing water changes so frequently. Any other advice would be great. Snails are running all over eatinf algea and fish seem happy.

        2. Avatar Jeff Kurtz says:

          It’s my pleasure, Evan! I think you might be right that it’s just a waiting game at this point. As long as you’re providing stable parameters, good oxygenated conditions, adequate substrate for nitrifying bacteria to colonize, and an ammonia source, the cycle will get there eventually, though waiting it out sometimes takes the patience of Job. Keep us posted!

          1. Avatar Evan says:

            Hey one follow up,protein skimmers.Im guessing its still in break in phase. But still difficult to get the “bubble ratio” right. I lift it up higher on back of tank, seems to foam better but fills the tank with tiny little bubbles ive been told those can be harmful,other say its just annoying but will go away. Mind you it is (i think) a 60 HOB protein skimmer. But tank is only 36

          2. Avatar Evan says:

            Its a coralife skimmer. after raising it in higher in the water. Lesa bubblea but the chamber is still filled with bubbles i cant get clear at the bottom. Though it is cleaning. Just not sure how effective

  8. Avatar Evan Newsome says:

    Hey Jeff Kurtz, I was hoping you could help? I have a 36 gallon tank. Still trying to go through cycle,I had made mistakes early on, and did a fish in cycle.I grew up doing it that way not knowing as an adult there was another way.I digress, I had live rock in first then 4 fish. Its been over a month. i added bio start up earlier on as well, hoping to speed process and achieve decent levels of ammonia etc.

    My issue is my ammonia is at 0, nitrites and nitrates are peaking on my levels chart,but its been like that for over a week now. ive tried to vaccum as much old food as i can find and cut back feedings. only my live rock has brown thick tough algea. What can i do to get this cycle finished and the nitrites down?


  9. Avatar James says:

    Hi, Great webpage, it’s been very helpful. I have just filled my 91L aquarium with salt water (obviously) and 10kg of real reef rock (reef friendly & pest free) then added live sand (9kg) and Seachem Stability to help establish the bio-filter. However, i have not put anything into my media basket yet. I understand filter floss should be at the top to catch detritus and aware of other media’s on the market but which ones would you recommend and when do i add these, during cycling or after? My aquarium is an all-in-one system, Thank you 🙂

    1. Avatar Jeff Kurtz says:

      Hi James! Opinions vary widely on the use of various media. With the exception of bonded filter pad for mechanical filtration, I actually don’t use any type of media on a routine basis, preferring to use them only if a specific problem arises that I can’t seem to manage through water changes and protein skimming. In any case, I would hold off adding anything until after your cycle is established.

      1. Avatar James says:

        Okay Jeff, that sounds good enough to me. Just thought i’d get a second opinion regarding when to add the media, Thanks!

  10. Avatar TLee says:

    Hello Jeff, and everyone else!

    I have a 20 gallon IM Nuvo Abyss drop-off and it is in it’s third day of cycling. I was doing my tests this evening and my salinity was above 1.028 and I can not do a water change until tomorrow evening. Will this be harmful to my cycle process and if not could I hold off on doing the water change until my tank cycles. Thank you in advance for your response!

    1. Avatar Jeff Kurtz says:

      I would go ahead and adjust the specific gravity down to a level closer to natural sea water (i.e., around 1.025) or wherever you plan to keep it long term (for instance, some folks keep the SG lower than NSW in a fish-only system). With cycling only in day three, doing so shouldn’t upset the apple cart too significantly.

  11. Avatar Pete says:

    Great post! Even better comment replies!
    I currently am on day 7 of my 29g saltwater cycle with live sand and live rock. Today I’m going to be taking a water sample into my local fish store, as well as testing for the first time at home, and doing a water change. After reading through your comments and replies, I have a much more level headed approach to this ordeal.
    There are still LOTS of questions I have about what to expect and how long the conditions will effect my tank. But, I have no doubt I’ll find the answers I need here!

    Thanks a tank load

    1. Avatar Jeff Kurtz says:

      It’s our pleasure, Pete, and thanks for your kind words! Keep us posted on your tank’s progress!

  12. Avatar Chris says:

    Hello – I started a 65 gallon tank 4 days ago. So far I’ve added sand, salt water (mixed with instant ocean salt) & 62 lbs of pre-cured live rock from a local fish store. My salinity levels were initially too high, but I’ve gotten them down to 1.028 so far by taking out saltwater and adding RO fresh water. My question comes in regard to the cycling process. I tested the water today and did not detect any trace of ammonia or nitrite, however the nitrate level is around 40 or 50. I would have expected the ammonia levels to be high at this stage. Any recommendations or insight would be greatly appreciated!

    1. Avatar Jeff Kurtz says:

      Hi Chris! Your high nitrate level strikes me as odd since that’s the end product of nitrification and shouldn’t be appearing if you haven’t registered any ammonia or nitrite yet. I wonder whether it’s being introduced in some other way–in your source water perhaps?–or your test kit is potentially outdated and giving faulty measurements.

      On the other hand, I’m not really surprised that you haven’t started measuring ammonia or nitrite yet, as it’s only been four days, and the process can take several weeks. Keep testing for a while, and you should see spikes in these compounds. If that doesn’t happen for some reason, you can always add ammonia to the tank (e.g., in the form of decomposing fish food) to get the cycle started.

      Also, you’ll want to keep working on bringing your specific gravity down. It should be closer to the vicinity of 1.025.

      Keep us posted on your progress or if you run into any further snags.

      1. Avatar Chris says:

        Hi Jeff. Thanks for the quick response! I’ve gotten my specific gravity down to 1.026, so I think I’m doing okay there (I’ll still work on getting it to 1.025). I asked an employee at the local fish store about not detecting any ammonia or nitrite and she thought it was possible that the nitrification process had already been established in the first few days and I just missed it because I didn’t test until day 4. This struck me as unlikely. Does that seem possible to you?

        1. Avatar Angie says:

          Hi, I need some help. My 29 gal salt is high. 1.3…I’m doing a 5 gal water change. How much salt should I add to make the level go down?

          1. Avatar Jeff Kurtz says:

            Hi Angie! Do you mean the specific gravity is 1.030? (I think a zero is missing.) To bring the salinity level down, you’ll need to remove salt water and replace it with an equal volume of purified fresh water. You definitely don’t want to add any more salt at this point. Are you compensating for evaporation using salt water or fresh water?

          2. Avatar Angie says:

            Yes, I forgot the zero. 🙂 i wasn’t compensating for the evaporation. Should I be adding fresh water everyday? Like a cup or something?

          3. Avatar Jeff Kurtz says:

            You’ll want to top off any water lost to evaporation on a daily basis using purified fresh water. Remember, when water evaporates, all the stuff dissolved in it gets left behind. So If you don’t compensate for evaporation or you top off with salt water instead of fresh, your salinity will continuously rise.

            There’s no set amount of fresh water that you need to add daily because that’s going to vary considerably based on the rate of evaporation, which is affected by humidity, air movement, etc.

            It’s a good idea to place some sort of mark (even a piece of tape will do), either on your sump or on your display tank, at the desired water level and then top off with fresh water to that mark each day.

        2. Avatar Jeff Kurtz says:

          Hmm, I suppose it’s possible, but to go through both the ammonia and nitrite spikes and begin accumulating nitrate at such a high level within four days strikes me as unlikely.

  13. Avatar Jeff says:

    Hi sorry to bother you but I’m having some issues with a new set up and can’t figure out exactly what to do. I purchased some live keys sand and (pre-cured) live keys rock along with bagged aragonite. I made a mistake and listened to some people who said that the tank would cycle in a day and also ordered several blue leg hermits, detritus eating snails, 1000 pods, and macro’s all of which arrived at the same time. My first problem was a sand storm in the tank that didn’t resolve for a week. After this, I apparently had a significant die off which caused my ammonia to go sky high. Everything was proceeding at that point. Ammonia came down, nitrites went up. About a week ago I began to notice the tank clouding up again. At this point my nitrites began coming down and my ammonia was low, although not zero, about 0.25. This turned into a full algae bloom. I tried a 48 hour blackout which did not help. Yesterday the lights came back on and I retested. The ammonia is still low at the same level but not zero. Nitrites are down to 0. Nitrates are about 5. I use RO water, and have been feeding very sparingly. The remaining inverts and macros are doing well. My pods are reproducing, etc. Not sure where the ammonia is coming from or how to get rid of the bloom. I have a 54 gallon corner bow front. Please advise. Thanks, Jeff

    1. Avatar Jeff Kurtz says:

      Hi Jeff! It’s no bother at all! Essentially, your bioload has gotten ahead of your biofilter here. Remember, even when using pre-cured live rock, additional die-off occurs that continues to produce ammonia. In fact, as I mention in the post above, I often take advantage of that die-off to cycle new systems. However, it still takes upwards of a few weeks or more before I’m testing zero ammonia and nitrite. Anyhow, the ammonia you’re measuring can be attributed to tentative biofiltration coupled with that continued die-off and the premature addition of livestock.

      At this point, you need to allow the biofilter to catch up. So you definitely don’t want to add any more animals and should feed very sparingly, if at all. You might also want to explore the possibility of adding a product that contains live nitrifying bacteria, such as Bio-Spira, to help the cycle along. I’ve never used these types of products myself, and not all of them are worthwhile, but Bio-Spira has a pretty solid reputation in the hobby. Just something to think about.

  14. Avatar Angie says:

    Hi! I set up a 29g bio cube today and I’m hoping you can help me out. I am a newbie and want to get this right. I have live rock and gravel right now in the tank. Should I add sand? What do I do now? How often should I check levels?

    1. Avatar Jeff Kurtz says:

      HI Angie! Unless you want to have a mixed substrate for some reason, there’s no need to add sand on top of your gravel. At this point, I would just get everything running as it will be when the tank is stocked (with the exception of the lights–they aren’t necessary right now), making sure there’s good water movement in the system and that the salinity and temperature are in the desired ranges. Then start testing the water. I usually test two or three times per week when I’m cycling a new system. Once both the ammonia and nitrite levels have spiked and fallen back to zero, it’s safe to begin stocking–albeit very slowly and gradually. Remember, it’s very easy to overwhelm a tentative biofilter by introducing too many specimens or adding them too quickly!

      1. Avatar Angie says:

        Thank you so much for your response Jeff. So I have a question regarding the back compartment. I’ve read many for him so it’s a bio balls are not needed if you have live rock which I do so what exactly do I need to make sure that I have back there? Right now I have a skimmer in Chamber 1. This is of course turned off since it’s still cycling. I have nothing in the middle chamber and I have the pump and chamber three. I do have a 500 pH powerhead in the tank attached to the glass. Do you think that’s enough for circulation.

        1. Avatar Jeff Kurtz says:

          My pleasure, Angie! You definitely don’t need (or want) to use bioballs along with live rock. The rocks will provide all the biofiltration you need (assuming you’ve got enough of them, of course).

          As far as the middle chamber is concerned, perhaps you could use it for your heater or chemical filtration media, such as activated carbon. I’m picturing the biocube from memory (never actually used one), so perhaps some other folks out there who currently have the system could chime in here?

          Your 500GPH pump should be sufficient, though makes and models vary considerably in efficiency and reliability. What type of pump is it?

          1. Avatar Angie says:

            I added a filter block on the middle, I saw a post where some people have hem there.i don’t currently have a heater, I live in Phoenix and thought I may be okay weather wise.

  15. Avatar brett bertschinger says:

    Do you have to cycle a new tank with salt added? Or can it be added after you get the appropriate parameters?

    1. Avatar Jeff Kurtz says:

      Thanks for your question, Brett! You’ll definitely want to add salt to the appropriate salinity level before attempting to cycle your tank.

  16. Avatar Shawn says:

    Hello everyone, got a couple questions here I have a 36 gallon salt water tank gonna get a reef tank goin I have added the live rock and and crushed coral just wondering if I’m supposed to have my filter on i do atm. And also I had a lot of purple on the live rock I had but it is mostly turning green and dying off will it come back? There is still some purple left but I havnt seen much action other then that goin on and havnt done any tests yet since I’ve been working to much lol ..

    1. Avatar Jeff Kurtz says:

      Hi Shawn! When setting up a new tank, I always run everything as it will be when the system is stocked, with the exception of the lights. The coralline algae should come back as long as you’re maintaining proper water parameters (calcium/alkalinity, etc.).

  17. Avatar Jacqui Potgieter says:

    Hi I need your help. We inherited a huge marine tank when a restaurant next to ours closed down. As I have no clue when it comes to marine tanks ( but I have kept tropical tanks all my life) I contacted a marine care ” specialist ” to assist with the move from the restaurant to our home. The process has taken much longer than anticipated due to their frequent stalling and many excuses.

    Nevertheless We now have the tank at our house. They filled it with saltwater and bacteria on 23 December and we were told it needs to cycle for 2 weeks and they would come back on 6 January to complete the installation ( at this stage there is plenty live rock, water and wave makers in the tank – nothing else). They have again stalled by saying the will come “tomorrow” with every call I make and are now not answering my calls.

    My problem is I am becoming very concerned as there is no filtration system in place, the tank has huge amounts of brown algae growing and I am really worried that we are going to loose the 2000 litres of water.

    The tank was a fully functioning operation at the restaurant so all the equipment is there but I have no idea how to set up the filtration system. How much damage can that algae do to the water?

    They also have all the fish at their establishment that were originally at the restaurant and have been ” babysitting them” for almost three months.

    I need to get this tank up and running ASAP.

    The really came highly recommended so I am in utter shock
    Thanks Jacqui

    1. Avatar Jeff Kurtz says:

      Hi Jacqui! I’m sorry to hear about your frustration! The algae, while unsightly, won’t harm your water in any way. It’s just taking advantage of dissolved nutrients.

      As far as filtration is concerned, it’s most important to have good biological filtration in place–meaning the tank is fully cycled and there’s no measurable ammonia or nitrite–before any livestock can be safely added. Assuming the original tank was torn down and moved expeditiously and proper water flow, temperature, and chemistry are being maintained in the new location, it shouldn’t take all that long to get the biofilter re-established. Still, you’ll want to monitor the ammonia, nitrite, and nitrate levels to be sure before reintroducing the fish.

      Does the system come with a protein skimmer? That’s the one piece of filtration equipment the tank really must have in my opinion.

      Keep us posted on the tank’s progress, and if there are any more questions we can help with, just let us know.

  18. Avatar Jessica says:

    Set up a 26 gallon hex tank a little over a week ago. I have live rock from a friends sump and I have been adding bacterial supplement to the tank. All my reading are great except for the ammonia , it is reading 0.50. I did a 10 gallon water change and added some more live rock last night with a sample bottle of a kick start tank cycler. I was told to wait 24 hrs and test again. Results are exactly the same. Nitrite and nitrate 0.0. PH 8.2 and ammonia 0.50. Any ideas on how to get it to go down?

    1. Avatar Jeff Kurtz says:

      Hi Jessica! At this point, you’ll just need to wait while the population of nitrifying bacteria catches up. Remember, it can take several weeks for the cycling process to run its course.

  19. Avatar Lindsey says:

    Hi I am new at this saltwater aquarium stuff but I have a 25 gallon tank and I test ny water my ph is still low and nitrite getting better what are the test results I should have for nitrite salt nitrate and ph? Also when I can start what corals can I have with sea anemones that will get along together with clown fish? Sorry so many questions just really excited.

    1. Avatar Jeff Kurtz says:

      Hi LIndsey! You’ll want to make sure your tank is fully cycled before adding any livestock. That means the ammonia and nitrite levels should be zero and the nitrate level should as low as possible. Since you plan to keep invertebrates, I would shoot for a specific gravity of 1.025 and pH somewhere between 8.2 and 8.4.

      I wouldn’t recommend trying to keep an anemone in a tank that size, especially with corals or other sessile invertebrates (anemones wander and can easily sting/get stung by neighbors in such close proximity) No worries, though. Clownfish do just fine in aquariums without a host anemone.

      1. Avatar Lindsey says:

        Thanks for your help!!

        1. Avatar Jeff Kurtz says:

          My pleasure, Lindsey!

  20. Avatar Charlotte says:

    Hi. Just started cycling my 120 gallon tank today with live rock. Are there any visible physical changes that I need to be looking for in the tank? I am aware of all the chemical changes but have not read anything about physical changes. Will there be anything growing that I need to be looking out for?

    1. Avatar Darren says:

      Not to sure how to answer your question but if your on Facebook there are loads of marine groups that offer advice on almost anything u need to know I use them for anything am not sure about

    2. Avatar Jeff Kurtz says:

      Hi Charlotte! The only physical things you might want to keep an eye out for at this stage of the game are, perhaps, Aiptasia spp. anemones appearing on the rocks or any other nasty stowaways (e.g., crabs or mantis shrimps) that make their presence known, Apart from that, you’ll just want to monitor the progression of ammonia to nitrite to nitrate so you know when it’s safe to begin stocking.

      1. Avatar Charlotte says:

        Thanks. I have started seeing some brownish stuff on the sand. Is this algae? How do I get rid of it? Is it harmful or normal during the cycling process?

        1. Avatar Jeff Kurtz says:

          The brownish growth is probably a diatom bloom, which is normal after a new system gets up and running. It’s not harmful and should eventually wane on its own–though it is rather unsightly and may necessitate some glass scraping. I like to equate diatoms in a new system to stepping in a mud puddle with a brand new pair of tennis shoes.

          1. Avatar Charlotte says:

            Not fun. So is there anything that I am doing wrong or not doing yo cause this?

        2. Avatar Jeff Kurtz says:

          Nope, it’s just a normal part of the process. Every tank I’ve set up has gone through a diatom bloom in the early stages. You might also go through cyanobacteria and hair algae blooms, but again, they’ll gradually dissipate as whatever is fueling them gets depleted.

          1. Avatar Charlotte says:

            During the cycling process, should I scrape the brown algae off the glass or rocks?
            Also, here are my readings today for my tank that I am cycling:
            PH: 8.2
            KH: 4.3
            Ammonia: .4
            Nitrates: 3
            Temp: 78
            Salinity: 1.025

            Am I doing ok? My tank is 120 gallons with live rock and sand. Been cycling one week

        3. Avatar Jeff Kurtz says:

          By any chance, do you have the nitrite and nitrate readings reversed in your list? I ask that only because at this stage of the game, it would be more likely to see some nitrite and 0 nitrate. Apart from that, just keep doing what you’re doing until both ammonia and nitrite are undetectable. Then, if you have nitrate accumulating, you can perform a water change to bring it down and then start stocking very slowly and gradually.

          As far as the diatom growth is concerned, you can go ahead and scrape it from the glass if you like, but I’d just wait it out on the rocks. Brushing them off at this point would likely just disrupt the cycle that’s becoming established. It’s definitely unsightly, but it should run its course and start to wane.

          1. Avatar Charlotte says:

            Week one of cycling is over now going into week 2. Here are my readings for today:
            PH 7.6
            KH 3.9
            Ammonia .4
            Nitrates 5
            Nitrites 0
            Salinity 1.025

            Lots of brown algae on sand, rocks and glass of aquarium.
            Am I doing ok?

  21. Avatar Wayne says:

    Hi Jeff,

    I have just bought a 4ft x 1ft x 2ft tank, and have added dead rock and 35 gallons of salt water from my LFS. Should I have the skimmer/filtration systems working before I add live rock, or are they ok to be off now and just move the water around with a pump?


    1. Avatar Jeff Kurtz says:

      Hi Wayne! No need to run the skimmer/filtration prior to the addition of live rock. As long as you’ve got good circulation and proper water parameters, you should be in good shape.

  22. Avatar shal says:


    I got a 50G tank and its been cycling about a week with live rock and cultured sand, however the ammonia reading is low, I have been putting fish food in it to decompose and to get the ammonia going. How long can I expect for the ammonia to go high and the cycle to start? Will this prolong the process of cycling?

    1. Avatar Jeff Kurtz says:

      Hi Shal! There’s really no set time frame for cycling since there are so many different factors that can affect the rate. I’ve seen the whole process take anywhere from just a few weeks to a month or even longer. As long as you’re providing an ammonia source, good oxygenation, and substrate to colonize, the bacteria will kick in and do their job. Adding the food shouldn’t prolong the process. In fact, just the opposite should be true.

  23. Avatar chris says:

    Hi jeff, I’m pretty new to this hobby .I bought a 28gal nano-cube that was already established, all parameters looked fine for about a month ,then I noticed the ammonia levels getting high .I performed several 5% water changes , with no success of bringing the level down.i proceeded to do a 10 gal water change which I’m pretty sure put me in a cycle. Right now my parameters are Ammonia =8.0 Nitrite=5.0 Nitrate=160ppm . Is there anything I can do or will this straighten out with time?

  24. Avatar Darren says:

    Can u add live rock after cycling ?

    1. Avatar Jeff Kurtz says:

      Hi Darren! You can add live rock after cycling, but in that case, you’ll need to make sure any die-off takes place in a separate vessel before the rock is moved to your display tank. Otherwise, you may get an ammonia spike in your display to the detriment of any inhabitants.

  25. Avatar Karthikeyan says:

    Hi there this question may be thoughtful
    Can I use a cycled freshwater tank to change into saltwater tank and just add fish?

    1. Avatar Jeff Kurtz says:

      I’m afraid not, Karthikeyan. The nitrifying bacteria that provide biological filtration in a freshwater system wouldn’t survive the transition to salt water. Not to mention, you’d probably want to change other aspects of a freshwater tank before making the switch, such as the substrate, tank decor, etc.

  26. Avatar PrazAU says:

    hi Jeff

    I have another thing to clarify . I found that “water will evaporate from the tank and need to be replenished. The water that evaporates is freshwater and needs to be replaced with freshwater. You should never use saltwater for makeup water (unless you want to increase the salinity of the tank). ”

    Is this correct? I am confuse now. So does this mean when I see that water has been evaporated after two or three days I need to refill with freshwater.

    What about when do water change ? I guess I have to use salt water

    1. Avatar Jeff Kurtz says:

      Yep! You’ve got the right idea! Remember, when salt water evaporates, all the stuff dissolved in it stays behind, so fresh water must be used to compensate for evaporation.

      In contrast, when you physically remove water (for example by siphon) during a water change, all the dissolved stuff goes with it, so you need to replace the water you’ve removed with salt water of the same salinity/specific gravity.

      1. Avatar PRaz says:

        G’day JEss

        I added one Damsel to fish salt water tank and fingers crossed 🙂

        Hopefully this will speed up the tank cycling process

        Just want find out do I need to keep lighting on all the time. I guess lighting more required if I have corals in the tank

        Is it ok to running lighting probably 6 hrs per day in FOWLR system?

        1. Avatar Jeff Kurtz says:

          Good morning! Keep in mind that adding that damsel could lead to compatibility issues when you begin to add more livestock. Many of the damsels are highly territorial and will claim an entire aquarium (especially a small one) as their own. Thus, they’ll be inclined to attack any newcomers. You might need to remove the damsel if you plan to add more fish. Though, again, with such a small system, you don’t have a lot of leeway in this regard.

          As far as the lights are concerned, 6 to 8 hours per day is just fine for a FOWLR system. As you note, with photosynthetic invertebrates, a longer photoperiod is necessary–typically between 10 and 12 hours per day. Of course, high-intensity reef-quality lighting is also essential if you plan to keep photosynthetic corals or other invertebrates.

  27. Avatar PrazAU says:

    G’day Jess

    Other than keep eye on mmonia , nitrites,PH and nitrates how do I check suitable salinity on salt water tank

    I am already using salut water got from local aquarium

    Do I still need to test salinity before I introduce first fish ?

    1. Avatar Jeff Kurtz says:

      Here’s a link to a post we did on mixing saltwater that might give you some helpful insights:

      As with all water parameters, you definitely want to keep the salinity stable and test it regularly with a good hydrometer or refractometer. And it is very important to check your parameters before adding livestock to ensure all the levels are where they should be.

  28. Avatar PrazaU says:

    Thanks Jeff


  29. Avatar PrazAU says:

    hi Jeff

    I setup 65 Saltwater Tank live rocks,sand,protein skimmer adn filter media yesterday .

    Do I need to add heater to get this process?

    Also may be stupid question . Can I use my API fresh water kit to check water parameters ?

    Or should I get API salt water kit ?

    Also is ok add one fish to speed up the process ? If that ok what fish?

    Thanks very much

    1. Avatar Jeff Kurtz says:

      Hi PrazAU,

      Unless the air temperature where you live makes it unnecessary, I would go ahead and add the heater. With respect to water testing (not a stupid question at all!), you’ll need to use the saltwater kits to monitor your parameters.

      I would advise against adding a fish to speed the cycling process along. Some amount of die-off will occur on the live rock, which should provide enough ammonia to get the cycle established. If you begin testing, you should detect a rise in the ammonia level soon, which will then drop as it’s converted to nitrite. The nitrite will then spike and drop as it’s converted to nitrate. Once you get readings of 0 for both ammonia and nitrite, you can go ahead and start adding fish–slowly so the nitrifying bacteria can keep pace with the increasing bioload.

      Hope this helps!

      1. Avatar PrazAU says:

        hi Jess

        Thanks you so much for prompt feedback. What sort of temperature level should I set it up the tank while it’s cycling ?

        Also do I need to do 10%-35 water change weekly while it’s cycling ?

        Also is it ok to add more live rocks ?

        1. Avatar Jeff Kurtz says:

          I always set the temperature where I plan to maintain the system long term–usually somewhere between 76 and 78 degrees F.

          I don’t usually perform water changes during cycling, but there are varying opinions on that. Some hobbyists perform them during the process to prevent excessive ammonia from killing critters in the live rock. However, most of the live rock I’ve used for cycling has undergone very minimal die off, so the ammonia level never gets particularly high.

          If you plan to add significantly more live rock, I would suggest doing so now. Otherwise, the consequent die off that will occur on the new live rock could cause another ammonia spike down the road, which would be problematic once you’ve begun to introduce livestock.

          1. Avatar PrazAU says:

            Thanks for your valuable feedback Jeff

            Also at what point I should add some corals . I have heard about different types of corals Ex soft corals

            What’s you you suggest for 65l nano type tank

          2. Avatar Jeff Kurtz says:

            My pleasure! You can begin adding corals as soon as the cycle is established and as long as your dissolved nutrient level is sufficiently low. Of course, with such a small system, you’ll definitely be limited in the number and size of corals you can introduce. Our friends at Live Aquaria have a section devoted to nano-sized corals at the link below that you might want to check out.


  30. Avatar Matt Filippi says:

    At the end of the cycle…ammonia and nitrites at zero, nitrates through the roof…160.

    Will nitrates eventually come down over time?

    1. Avatar Jeff Kurtz says:

      Hi Matt! That really is a sky-high nitrate reading. Are you certain that’s accurate? To bring the level down, you’ll need to perform a major water change (using source water that isn’t high in nitrate to begin with–ideally RO/DI-purified water) or utilize some type of nitrate-adsorbing filter medium or nitrate reactor. But it might be helpful if you can provide more details about your system–size, how you cycled it, etc. Also, are you sure the test kit you used is fresh (as in not expired) and of a reliable brand?

  31. Avatar Matt Filippi says:

    Should the tank lights remain on during cycling?

    1. Avatar Chris Aldrich says:

      Hi Matt – There is no need for lighting during the cycle. Any light usage would be purely cosmetic and for your own enjoyment. So, it’s up to you. 🙂

      1. Avatar Matt says:

        Perfect. Thank You.

        1. Avatar Chris Aldrich says:

          You’re welcome, and good luck with your aquarium!

  32. Avatar Kendra says:

    Great post. Thanks for sharing and keep posting.

  33. Avatar Pat says:

    My tank has never had ammonia,nitrate or nitrite levels above zero! My fish store recommended I add two “nemo” fish after a month of cycling with live rock and sand etc. after 2weeks with fish and feeding all para’s remain at zero. What should I do???

  34. Avatar Pat says:

    Sorry. I have 29G Biocube

  35. Avatar Jeff Kurtz says:

    Hi Pat! With two clownfish and their food in the system, you have a source of ammonia, so you really should be measuring some by now unless the tank had already cycled with the live rock. But in that case I would expect that you’d start to measure nitrate (unless you already have really efficient denitrification going on, which is questionable in such a young tank).

    You might want to test with a different kit or ask your LFS to test the water to make sure you’re not getting faulty readings. Also, what sort of water-change regimen are you following? If it’s really aggressive and your tank isn’t cycled yet, you might be removing any ammonia before nitrifying bacteria can get a foothold. On the other hand, if the tank was already tentatively cycled with the live rock, you could be diluting nitrate to an unreadable level. Just a possibility to explore.

    Also, keep in mind that cycling with fish is always problematic because now you have to strike a very delicate balance between poisoning the clowns with their waste products and getting the cycle established. Clownfishes and other damsels are generally tough enough to endure this exposure, but even they have their limits, so you’re always more or less working at cross purposes when cycling with fish.

    At this point, one option is to continue monitoring ammonia, nitrite, and nitrate very closely with a quality test kit and be prepared to change water to dilute ammonia to a safer level if it spikes. The tank will eventually cycle in this manner (if it hasn’t already), though the process may be painfully slow. And, of course, any further ilvestock additions should be made very slowly and methodically.

    Alternatively, you could temporarily rehome the clowns (e.g., by asking your LFS to hold them for you) and then introduce ammonia to the system by adding fish food to the tank daily and allowing it to decompose.

  36. Avatar Pat says:

    I did a 10% water change before adding the fish.and all param’s were good-am ,ni, na were still zero. Went on vacation for 1wk grandkids fed fish for me. All param’s good except Kh dropped from 12 to 10 – am, ni, na still zero and green hair algae is on the rocks. I started to feed a little more food in hopes of allowing some decay to increase ammonia that way. Any other suggestions? Is this ok?

  37. Avatar Jeff Kurtz says:

    At this point, I think I’d just feed the appropriate amount for the fish, keep up with the weekly partial water changes, and keep a close eye on your ammonia, nitrite, and nitrate levels. With the fish in there, ammonia is being produced, so it may be that there’s enough biofiltration going on to convert what’s present. But again, stay vigilant against a potential ammonia spike and after a while you should be able to proceed very slowly and methodically with further livestock additions.

  38. Avatar Pat says:

    Thank you. Love your website!

  39. Avatar Jeff Kurtz says:

    My pleasure, Pat! Thanks so much!

  40. Avatar Jeff Kurtz says:

    Not a stupid question at all! I would go ahead and add the heater and set it for the temperature you plan to maintain long term.

  41. Avatar Armando says:

    Please help

  42. Avatar Jeff Kurtz says:

    Hi Armando! How can we be of assistance?

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