Test kits.

Don't lose any sleep over the condition of water in your tank until you have test kits, so that you know what to be fretting about! Your basic information on test kits is at theKrib.com, once again. Test kits are essential. You might not want any more than the basic series, which--— most of us would agree-- are tests for pH, ammonia, nitrite and nitrate. I'd add to this kit the tests for general hardness (GH) and for alkalinity or buffering capacity, generally referred to as "carbonate hardness" (KH).

You might add a test for chlorine, including the chlorine bound in chloramine. Whether sold to pool-owners or aquarists, there are two chlorine testing reagents on the market today, OTO (reacts as yellow) and DPD (reacts as pink), about equally sensitive, to about 0.1 ppm chlorine/chloramine. They're cheaper among the pool supplies at Home Depot, though not if you're making a special trip.

A badly-run test is worse than no test at all. More misleading. When you test, follow the directions in every last detail. Rinse your container before and after every test. (Don't get in the habit of pouring the rinsewater back into the tank: you'll regret it one disastrous day.) Don't take the surface scum into your test vial; the extra proteins and lipids, etc. may give you a mis-reading. Measure accurately. Measure water by the flat area of the surface, not where surface tension makes it creep up round the edges. Invert the test solution bottle quickly and smoothly, and don't let it touch the test vial, to get accurate uniform drops. Shake test solutions diligently when required; think how good it is for muscle tone. Use the test vial's cap; don't substitute your thumb: it carries oils and acids that could affect the readings, and besides, some test solutions are toxic or caustic. In some tests, the resulting color takes some minutes to develop; wait for results to show, if need be.

On the other hand, don't obsess over the exact numbers you come up with on each test; keep an eye more on the direction of trends. Testing for ammonia or nitrite is a case in point. Actual numbers are academic: the only "okay" levels are undetectable. If there is any ammonia or any nitrite in an established system, you have an emergency to deal with. On the other hand, there is probably going to be some level of nitrate. Less than 40 ppm in a freshwater system is okay. Nitrate levels in a planted aquarium can be lower, even less than 10 ppm; but sometimes hearing that an established tank has 0 ammonia and 0 nitrite, yet also 0 nitrate, tempts me to suspect that there are flaws in the testing procedure. As a rule, there is generally some detectable nitrate in an established system.

Jared W's test-kit primer. This is at Jared W's plant-oriented website. Go and look now. Bookmark it. You're going to need it.

Nitrate tests. When nitrate test results are higher than about 40 ppm, it may be difficult to get an accurate reading. If your nitrate levels are so high you can't really tell red from red from red, extend your testing range simply by diluting your test water. Carefully measure 5ccs of tank water and put it in a second test vial. Measure out 10ccs of distilled water and mix with your test water. Measure out 5ccs of this diluted sample to test with. Afterwards multiply your nitrate reading by 3. This is a good way to doublecheck your usual results. ...By the way, if your testing sample needs to be diluted, so does your tank water, I'd bet. Step up the water changes.

Ammonia tests. There are two basic types of ammonia test kits. Nessler kits have one reagent, that is, a single bottle of liquid or one tablet to dissolve in your water sample. If your ammonia test kit registers in shades of amber, it's Nessler. They generally are quicker to use, but ammonia-locking products (e.g., AmQuel) will cause Nessler kits to give false positive readings.

The other type of kit is salicylate based, with two sets of reagents. If your ammonia test kit registers in shades of yellow to green to blue, it's salicylate. Salicylate test kits are unaffected by AmQuel and similar products, but they do take longer to develop a reading. If your water has chloramines and you're using AmQuel or somesuch, you'll need a salicylate NH₃ test.

Don't test for ammonia right after a water change. If you're too liberal with the dechlorinator, you could be getting some false-positive ammonia test results that way, too. According to Seachem at their website, harmless sodium thiosulfate, such as found in Seachem's Prime conditioner, will give false positive readings for ammonia, whether the tests are based on Nessler's Reagent or on salicylate. What happens is this: the sodium thiosulfate, Na₂S₂O₃, is reacting with the chloride ion that is part of the test reagents. After 24 hours, though, according to Seachem, the Na₂S₂O₃ will have have reacted with chloride ions naturally found in water, and will no longer give such false-positive readings.

pH tests. Probably your pH test kit will be based on bromthymol blue. (Litmus papers aren't accurate enough for aquarium use.) With practice, if you have a good color eye, you'll see the difference between, say, pH 6.4 and pH 6.6 at a glance. I like the rectangular test vials because I can get a more saturated hue by sighting through the test vial the long way. An additional drop of bromthymol blue will usually intensify the color, if you have doubts about how to read the result, without affecting the hue. Try this yourself, cautiously

A repertory of indicator dyes cover the whole gamut of the pH scale. Only a few are used in aquaria of course. The familiar "low range" pH reagent, Bromthymol Blue, tests in the range pH6.2-7.6-- a mid-range, really. However, if your pH test result using Bromthymol Blue registers one extreme value or the other, the test may not have reported the actual pH, which may in fact lie beyond the test's range. (Don't confuse Bromthymol Blue with Thymol Blue, which tests in the range pH8.0-9.2.)

I lurk at several aquaristic web forums and read of fishkeepers' reported troubles, and I'm aware how often the pH in question is reported as either 6.2 or 7.6, which are simply the endpoints of the common "low-range" pH kits based on Bromthymol Blue.

You won't make this mistake. If you're getting either of these endpoint values, you should retest with indicators more appropriate to the range.

For instance, if your Bromthymol Blue test registered pH 6.2, you might consider retesting with a lower-range pH kit, using the indicator Bromcresol Purple. It's orange at pH 5.0; at pH 4.8 or lower, the dye turns yellow; from pH 5.5 to 6.4, the color of the dye is red; above pH 6.4, it becomes purple. (Another cresol dye, m-cresol, tests pH in saltwater.)

Or, in alkaline ranges, to get a genuine reading above pH 7.6, you'd be using a "high-range" pH kit, with a range pH 6.8-8.0, which is based on Phenol Red, reacting from red to yellow. This kit is more familiar and you'll find it at the LFS.

Kordon offer a good view of their Aqua-Tru pH test kits, with powdered reagents sealed in foil packets, at their website. They claim that their Low Range Bromthymol Blue kit tests as low as pH 5.5.


Phosphate tests. Test equipment that has not been soaked in dilute HCl (muriatic acid) and rinsed in distilled water, will be contaminated with sticky phosphate residues from the previous test. Or from PO₄ in the tapwater it's been rinsed with. Professionals testing for phosphate don't let the test ampoules dry out even! Unless you are boiling your water sample with acid, your phosphate testing doesn't take into account any of the PO₄ that is organically bound or built into organic molecules. Decomposers, like bacteria and micro fungi are constantly at work, releasing this PO_4-- "mineralized"-- into the system once more. So phosphate could test higher two days from now, even if no PO₄ were added to the aquarium system.

A good description of the care involved in executing a test for phosphates that is not misleading is at Brad Woods' Bald Eagle site Run through it once to see the various ways you may be contaminating your own aquarium PO₄ tests.

My recommendation about amateur phosphate testing is, don't make decisions based on numbers you've got as test results.


Potassium tests. Potassium testing is not simple either. LaMotte makes a potassium kit in which you have to judge K levels by the turbidity of the testwater, not an easy call. You should run distilled water through a test procedure first, and subtract any result you get from your K test results. Frankly I'd think potassium tests are best interpreted simply as positive/negative tests. Some cloudiness in the test solution indicates some K. Some is all the system needs for today.

Fishkeepers with plenty of calcium in their water will tell you it's impossible to overdose potassium, but in my very soft water, where it's all too easy to upset the Ca:K ratio, I lightly dose the makeup water instead.

Storage. Test kits should be kept dark, dry (if they're dry) and cool. Dry reagents last longer than pre-mixed "wet" ones. Still, no reagents last forever; once the seal has been broken, oxidation sets in. Reputable test kits come permanently marked with lot numbers and expiration dates. Aquarium Pharmaceuticals is widely credited for dependable tests kits; the last four digits of their lot numbers represent the month and year of manufacture. AP suggests a "best if used before" shelf life of three years for nitrate, high-range pH and general hardness kits and five years for mid-range and ammonia kits. I had an Aquarium Pharmaceuticals Nitrate Test kit where the box was printed "Lot No. Exp. Date" but the actual date was printed on a peel-off sticker. I was not amused.

Most fishkeepers would agree that the Rolls-Royce of water tests is the Lamotte line. In their narrow-range pH test, for example, you will be comparing your test sample to eight sealed liquid reference solutions. Very elegant. See the Lamotte website for details.