Aquarium Test Kits
There are a large number of test kits available for the fishkeeper to choose from - but which ones
are worth having? Listed below are those which are considered the most important by the majority
of fishkeepers. This article is not intended to discuss the use and interpretation of the measurements
- see the separate articles linked below.
The most important test kits are:
Ammonia and Nitrite - to check that the biological filtration is coping with waste levels
Nitrate - to check that tank maintenance (mainly water changes) are adequate for the setup
pH - to determine how acidic/alkaline your water is
GH - to determine the general hardness of your water, i.e. the level of hardening ions like calcium and magnesium
KH - to detemine the carbonate hardness of your water, i.e. its 'buffering' capacity
Ammonia and nitrite kits provide reassurance that the biological filtration is adequate. These test
kits should be used to monitor cycling in a new setup, after any filter failures, when the fish stock is
increased significantly, or if there are any signs of problems in the tank. It is not necessary to test routinely for these two
once you are confident of your aquarium management skills, unless you prefer to err on the cautious side.
Nitrate testing should be an ongoing process, to provide reassurance that water changes are coping
with the build up. Remember that nitrate is also a useful indicator of the water quality in general - i.e.
other potentially harmful wastes may build up in the absence of water changes, nitrate
is simply a convenient one to measure. Remember that as the fish stock increases, and the fish grow, wastes will increase, so checking the nitrate
level will indicate whether the water change schedule is still sufficient.
The pH, GH and KH will provide information about the chemical nature of your tap water and tank water,
and help you to decide whether the water is suitable for the type of fish you wish to keep.
Others test kits which may be worth considering are:
Phosphate - an additional measure of waste levels in the tank. The sources of phosphate differ from
those of nitrate, and one may be high without the other. Excess phosphate is often implicated as an algae-causing nutrient.
Iron - useful for planted tanks, both for measuring the iron level itself, and as an indicator of the
general macro/micronutrient levels when using a fertilizer.
Marine fishkeepers will often use a wider range of kits, especially for reef tanks, to monitor a number of important
minerals (such as calcium) and trace elements.
Some experienced fishkeepers may be skeptical of the need for test kits. It is certainly true that the more
experienced one becomes in keeping fish, the greater the expertise in recognising small differences in the
appearance and behaviour of fish as indicators of water quality.
However, you do not have to be an expert to use test kits, and they can help to build up a feel for
water quality and fish health in relation to the measured parameters. There are also situations where
knowing the water parameters is vital (at least initially) - such as whenever water chemistry is being
modified, as when preparing RO/DI water for use. A knowledge of your water parameters is also useful
if you wish to pass on your experiences to other fishkeepers. For instance, if you have managed to breed
a difficult fish, telling someone on the other side of the world that the fish will spawn in tap water may
be of little use if their tap water is completely different. Stating the pH and hardness values is far more