Beginner FAQ: Test Kits
There is a seemingly endless array of test kits for testing
everything from ammonia levels to phosphate levels. Does one really
need to buy them? The quick answer is no. It is quite possible to
have a healthy tank without ever buying a single test kit. However,
test kits are extremely useful at eliminating guesswork when something
goes wrong (e.g., fish appear stressed or die). In the following, we
describe the test kits that are most useful and the conditions under
which they are useful.
Get one. Ammonia test kits are cheap ($5-10) and will tell you whether
your tank has elevated ammonia levels. This is useful in two
circumstances. First, during the tank-cycling phase, regular testing
for ammonia will tell you when the first phase of the nitrogen cycle
has completed. Second, should you have unexplained fish deaths,
testing for ammonia verifies that your biological filter is (or is
not) working correctly. Note that even in an established tank, the
biological filter can sometimes weaken or fail outright. Common
Which Are Useful?
Be warned: if you have fish deaths and subsequently ask the net
(or a fish store) for advice, the first question asked will be ``What
are your ammonia (and nitrite) levels?''.
- not cleaning the filter regularly (water can't flow through a
clogged filter, where the nitrifying bacteria reside),
- naively adding
fish medicines (antibiotics kill nitrifying bacteria (oops) as well as
disease carrying ones),
- having too small a filter for the fish load,
Ammonia levels are measured in ppm. At concentrations as low as
.2-.5 ppm (for some fish), ammonia causes rapid death
for further details).
Even at levels above 0.01-0.02 ppm, fish will be stressed. Common
test kits don't register such low concentrations. Thus, test kits
should NEVER detect ammonia in an established tank. If your test kit
detects ANY ammonia, levels are too high and are stressing fish. Take
corrective action immediately by changing water and identifying the source
of the problem.
Warning: Amquel and other similar ``ammonia-neutralizing'' water
additives are incompatible with most ammonia test kits. Water treated
with Amquel will falsely test positive for ammonia, even when ammonia
is not present. Test kits using the ``Nessler'' method are known to
give false readings under such conditions.
You might want to get one of these;
nitrite kits are cheap ($5-10) and are useful in the same
circumstances where an ammonia test is useful. The only time a nitrite
kit provides information that an ammonia kit can't is while testing
for completion of the second phase of the nitrogen cycle
(see the CYCLING SECTION). As in the
case for ammonia, if your test kits detects nitrite, your biological
filter is not working adequately. Once a tank has cycled, nitrite kits
are pretty much useless. (If the bio filter in an established tank
isn't working, both ammonia and nitrite levels will be elevated.)
Nitrite is an order of magnitude less toxic than ammonia. Thus, one
common saying about tank cycling is: ``if your fish survive the ammonia
spike, they'll probably survive the nitrite spike and the rest of the
cycling process.'' However, even at levels above .5 ppm, fish become
stressed. At 10-20 ppm, concentrations become lethal.
Get this kit! Nitrate levels increase over time in established tanks as the
end result of the nitrogen cycle. (The only exception to this rule is
heavily-planted tanks and some reef tanks,
which MAY be able to
consume nitrogen faster than it is produced.) Because nitrates become
toxic at high concentrations, they must be removed periodically (e.g.,
through regular water changes). Having a nitrate test kit helps you
determine whether or not your water changes are removing nitrates
Nitrates become toxic to fish (and plants) at levels of 50-300 ppm,
depending on the fish species. For fry, however, much lower
concentrations become toxic.
Note: A nitrate test kit is only of limited value in determining
whether the nitrogen cycle has completed. Most nitrate test kits
actually convert nitrate to nitrite first, then test for the
concentration of nitrite. That is, they actually measure the combined
concentration of nitrite and nitrate. In an established tank, nitrite
levels are essentially zero, and the kits do properly measure nitrate
levels. While a tank is cycling, however, a nitrate kit can't tell you
how much of the reading (if any) comes from nitrate rather than
Get one; these kits are extremely cheap, so there is no excuse for not
owning one. You will want to know the pH of your tap water so that you can
select fish whose requirements meet your water conditions. In
addition, you will periodically want to check your tank's pH so that you
can be sure it stays stable and doesn't increase or decrease
significantly over time.
In some cases, tank decorations (e.g., driftwood) or gravel (e.g.,
made of coral, shells or limestone) change the pH of your water. For
example, tank items may slowly leach ions into your tank's water,
raising the GH and KH (and pH). With driftwood, it is not uncommon to
have the wood slowly leach tannins that lower the pH.
You may want to get one of these, but having one is not
critical. You don't need to know the exact hardness level. Knowing
whether your water is ``soft'', ``very soft'', etc. is good enough. Your
local fish store may be able to give you sufficient information.
Alternatively, call your water utility (see the
TAPWATER SECTION of this FAQ).
This kit is not critical to have. By regularly monitoring the
pH, you can figure out whether your KH is ``high enough''. That is, the
KH should be high enough that your pH stays stable over time. If you
have trouble keeping the pH stable, you may want to increase your tank's
buffering capacity. Your local fish store may be able to give you
sufficient information as to your KH value. Alternatively,
A KH kit is, however,
indispensable to plant enthusiasts who use CO2 injection.
It is also strongly recommended that you get one if you want to change
the pH of your water, and it is a very useful diagnostic tool if you
are experiencing pH stability problems.