We’ve really been feeling it lately for nano tanks. We run much larger tanks for surgeonfish, but while we’re waiting for our Acros to grow in those we like to have some low-cost fun and set up nano tanks as well. Nanos offer much to reefers who are short on time, space, or money and are cheaper to set up, run, and stock, and much quicker and easier to maintain.
Nano Tank Size
For the purposes of this article, the kind of nano reef tanks we’re referring to are those in the 5-20 gallon/19-75 liter range. There is a new generation of truly tiny tanks holding just one-third of a gallon, but they must be treated differently as they can’t run the usual reefing equipment or house any fish. But choose any aquarium that’s upward of five gallons and there is a whole heap of fun, nano-sized equipment (and livestock,) that fit them. They don’t have to be bought as All-In-One saltwater aquariums either, as we’re gonna show you how to convert a super simple, bare, freshwater tank to run as a successful nano reef tank too.
Nano Tank Lighting
We are so lucky in 2023 to have the choice of small-sized lights on offer to us. It wasn’t always like that as before about 2005 the only small light available was a 12”, 8-watt fluorescent lamp from Rolf C Hagen, and no one even entertained being able to actually grow corals in small tanks. At the other end of the scale we used 150-watt metal halide lamps on open-topped nano tanks – imagine the heat – before compact fluorescents (still hot,) and finally LEDs came in.
Due to the nature of tiny LED diodes, LED light fixtures can be as small as you can imagine. If you don’t intend on light-loving corals then a lamp as small as five watts can be used on a five-gallon nano reef, right up to a 55-watt AI Prime 16HD, which would be bright enough for any coral in a small tank. Just as for larger tanks it’s all about par and spectrum, with a few extra features like app control and separate blue channels for pop. If you are one of the growing numbers of macroalgae gardeners then aim for the same range of wattage, but opt for a freshwater light instead, with a spectrum that has been selected to aid photosynthesis in freshwater plants.
Nano Tank Flow
All corals need flow, but this is easy and cost-effective to provide in a small tank. If you have the budget, select the smallest size DC wave pump you can find, and we have them going down as small as 264pgh/1000lph. A pump that size will provide 50 times turnover in a five-gallon tank, but a standard, old-fashioned powerhead with an inlet strainer will also suffice, or even an internal canister filter, which will double up as a filter too, offering mechanical, biological, and chemical filtration in a tiny package. If opting for a former freshwater tank, surface skimmers work well to remove the oily film of the surface of the nano reef as well as provide flow further down in the tank. And the best part, small pumps, powerheads, and filters are super low wattage and super quiet.
Nano Tank Heaters
Your nano reef will need to be heated, at the rate of one watt of heater power per liter of water, so a 75-watt heater for a 75-liter/20-gallon tank. Here, an AIO does come in handy as the heater can be hidden in the spacious filter compartment. If converting a freshwater tank, the heater should be placed inside the tank and hidden as best you can. All small heater/thermostats are marine safe and if you go really small, you can buy the tiny preset ones, which just heat to about 75F for 10 watts of electricity. Small tanks will heat and cool more quickly than larger ones and are susceptible to overheating in warm rooms. Tiny aquarium cooling fans are available, and even nano-sized chillers. Nano tank owners have never had it so good!
Filtration and nutrient control for Nano Tanks
Just like on a larger reef tank, we require zero ammonia and nitrite at all times, with nitrate at about 10 ppm and phosphate under 0.1 ppm. Ammonia, nitrite, and nitrate will depend on the creatures and food levels that you add to the tank. With a few tiny fish or no fish altogether and just tiny inverts, if you have a sand bed and some live rock, you won’t need any biological media. With no fish, you might not even need phosphate control, but if you do, again a simple internal canister filter, media bag stuffed into the back of an AIO, or a hang-on-the-back power filter will suffice. For larger AIO nanos and for those who want to invest, some nifty-looking, slimline phosphate reactors are available. Or you could provide flow, filtration, and nutrient control from an external canister filter, sat next to or underneath the tank.
Probably the coolest innovation in nanos right now are the third-party 3D printed nano rollers, made to fit popular makes and models of nano tanks. We’re not a big fan of sponges in reef aquaria so if your AIO comes with one, replace it with filter wool instead, add some ceramic media for biological, and simply throw the wool away when it gets dirty. It’s nutrient export 101.
Nano Protein Skimmers
If you don’t add fish, you won’t need a skimmer, but if your 20-gallon is stocked a little on the heavy side, a skimmer will certainly help with nutrient control and overall water cleanliness. Up until recently, all nano-sized protein skimmers were quite poor performers because they couldn’t provide enough air, small enough bubbles, or a long enough contact time to be effective. Recently we have seen some slimline DC-powered nano skimmers which are small enough to slot into the back of AIO, are very low wattage, and they skim. So they are worth looking into. If your tank isn’t AIO then tiny internal skimmers and HOB skimmers are available.
Auto Top-Offs for Nano Tanks
Nano reef tanks are super versatile and fun, but if they are open-topped, they 100% need an ATO. Just like with temperature, they are very susceptible to unstable salinity due to evaporation, and without stable salinity, you won’t succeed with a reef aquarium of any size. Nano-sized ATOs are available, we prefer optical sensors to float switches, and you definitely need them if the tank doesn’t have a tight-fitting lid. We recommend a purpose-built cabinet for any nano tank over 10 gallons, and they also make perfect storage for ATO reservoirs.
Auto Dosing for Nano Tanks
Unless you intend to do regular partial water changes, you’re going to need to dose your nano tank to buffer KH just as you would any larger reef aquarium. Equip the tank with a single-head auto doser and dose with KH solution or an All-In-One mixture, providing KH, Calcium, Magnesium, and trace elements from a single bottle. Go for a two-head doser and you can dose aminos too.
Saltwater Fish for Nano Tanks
Tank-bred clownfish will be the logical choice for many nano tanks, although all clowns really need a 20-gallon tank long term, and should be left out of smaller nanos. We feel all nanos are really too small for dwarf angels, wrasses, cardinals, and damsels too, but tanks of five gallons and over can make suitable homes for many gobies. Gobiodon spp. would work, Gobiosoma can be a little stroppy with each other, but the smaller shrimp gobies, Stonogobiops spp. and their accompanying Pistol shrimps could work really well in nano environments. With all the money saved in set up and running costs, you could push the boat out when it comes to livestock and invest in a pair of Yasha gobies, a Griessinger goby, or the recently renamed Lavender dartfish, Nemateleotris lavendula. If you want character, choose Plectranthias or Liopropoma…
Mobile invertebrates for Nano Tanks
A nano reef tank is where mobile inverts can really come into their own. Usually added to larger tanks to do a job, mobile inverts can be ornament as well as a janitor in small tanks where they can be viewed close up, and selected for color and pattern, the tank free of potential predators. Consider Pom-Pom crabs, Sexy shrimp, Anemone shrimp as well as hermit crabs and snails. Or what about a walking Dendro – a coral polyp that “walks” across the substrate courtesy of the Peanut worm underneath it? There is so much choice in invertebrates for the tiny tank, so search some out.
Corals for Nano Tanks
There really is no limit to what corals you add to a nano tank, as their needs can be met just as in larger tanks. If Acros or NPS corals are your thing then set up accordingly, and it won’t cost the earth if it goes wrong. That’s the joy of it. But frags really come into their own in nano tanks, and it shouldn’t take years for the tank to look full. Some people choose just Zoas for their nano, while others keep it super simple and easy with Green Star Polyp and pulsing Xenia. Go down the LPS coral route and Micro lords and Blastos work really well, as do Bowerbankis, Caulastrea, Duncans, Branching hammers, and branching frogspawns. A colorful, well-laid-out nano reef can be just as eye-catching and as enjoyable as a larger reef tank, for a fraction of the price and a lot less hassle.