August 6 2007,


To ensure that the water in your aquarium is up-to-par and meets the generally recommended standards for reef aquariums, regular testing is strongly recommended, not to say required.

By: Albert J. Thiel

This requirement is often overlooked by hobbyists who wait until something “does” not seem quite right in the aquarium before they actually perform any testing at all. At times, even then, they will not test. This is not a good practice at all, as we shall see in this article. One should test on a regular basis, and certainly when something is not right in the aquarium.

Often too, hobbyists will wait till undesirable algae appear before they actually start testing for nitrates, phosphates, and do something about silicates, to prevent the appearance of diatoms and brown algae. Note that nitrates are not really the cause of the outbreaks of algae but that phosphates and silicates are.

There are many other articles on algae, diatoms and slime algae on our web site in the Saltwater Library. You may wish to go there and read some more of those articles as it will give you a better understanding of the processes at work and how to deal with them.

Not testing until something is wrong is much too long a wait, of course! Water testing should be undertaken as a preventative measure, not as an afterthought or as a crisis management type action.

By testing on a regular basis many a crisis, and respectively problems, can be avoided. Stress on the animals, often leading to outbreaks of parasitic infestations will be avoided in that manner as well.

When the results of preventative testing show that one or more water quality parameters are out of line, immediate action needs to be taken to remedy whatever condition(s) need(s) to be corrected. In this manner aquarium and water quality problems that are harder to solve can be avoided before they occur. When one waits too long, the problem will be greater and more difficult to solve. Usually too, resolving the problem when it is more advanced, will become more expensive to boot.

Testing on a preventative basis not only saves money, but avoids many problems in the aquarium, e.g. high amounts of stress that lead to fish soon being found full of parasites, or contracting a bacterial infection or other form of disease. Any stress reduction is of benefit to all the animals in the tank. The less stress the less problems, it’s really as simple as that.

What should you test for and how often?

Listed, not in order of importance, are some of the tests hobbyists should be prepared to perform on a regular basis:

* Nitrate: as total nitrate. Recommended frequency: once a week. Note that most tests measure in N-NO3 and that to arrive at the total nitrate concentration, the result of that test needs to be multiplied by 4.4

* Phosphate: as ortho-phosphate. Recommended frequency: once a week. Only ortho-phosphate is measured, any other forms of phosphate in the tank are not. Tests for other forms do exist but are more expensive and are harder to interpret. They will usually test for total phosphorus.

* Dissolved oxygen: Recommended frequency: once a week. More often if the tank has problems and animals are suffering.

* Nitrite: once every two to three weeks after the tank has cycled. Before the aquarium has cycled: more often, to allow the hobbyist to determine when the cycle is completed. Test more frequently each time animals have been added to ensure that the bioload is not too high.

* Ammonia: once every two to three weeks after the tank has cycled. Before the tank has cycled: more often, to allow the hobbyist to determine when the cycle is completed. Test more frequently each time animals have been added to ensure that the bioload is not too high.

* The pH should be tested for frequently. Preferably several times a week, if not every day. This process should continue until the aquarium has stabilized itself, a process that can take several months. Ideally some kind of electronic meter is best because the results will be more accurate and the test faster and easier to perform.

* Hobbyists can now test for silicates as well. Up to very recently only real expensive tests could be obtained but, new ones – specifically for aquariums- are now marketed. In the initial stages testing should occur once a week. After the tank has stabilized itself every other week or so is recommended.

* Temperature: keep a close eye on the temperature every day. It is important that it not fluctuate too rapidly. Changes between day and night time are fine, as long as they occur gradually. Rapid changes induce stress. Stress leads to parasites and disease. When adjustments are necessary, make them real slowly.

* Specific gravity: test once a week in the initial stages and then once every two or so weeks after that. Do not let the specific gravity fluctuate too much. When adjustments are necessary, make them slowly. Rapid changes bring about stress.

* The carbonate hardness should be tested about every 2 to 3 weeks. More often if you have difficulty maintaining a high calcium ion level (the two interfere with each other). If the dKH is too high you will not be able to raise the Calcium ion level regardless of what you do. Even adding large amounts of Kalkwasser will only raise the calcium level marginally. If the dKH is over 7 or 8 it needs to be lowered.

* The calcium content. Check it about every week to two weeks. More often if your coralline algae do not grow properly. This could be because the dKH is too high or because the Calcium level is too low. The addition of Kalkwasser or another calcium supplement may be necessary, in addition to lowering the dKH. Note that if you are using a Kalk reactor you are dealing with a different set of parameters in terms of coralline algae growth not covered in this document. Should you have any questions regarding coralline algae growth you can send me a message.

* There are, of course, still other parameters you can check for:

o the redox potential
o the biological oxygen demand
o copper and other other heavy metals such as iron
o the components of the buffer
o lighting intensity at various spots in the tank
o and so on.

For now though, the above ones are the more important ones to check. They will give you a good idea how your tank is doing and what you need to remedy (if anything).

An important note: when changing water, make sure that the parameters of the water you add to the tank are the same as the ones of the water already in the tank. This applies especially to pH, dKH, temperature and specific gravity. In reef tanks, calcium levels should be the same too.

This may require that you adjust the water quality parameters of the water you are going to add to the tank, before you actually add it.


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