Test kits and aquarium and pond water testing

Why test the aquarium or pond water?

The best reason to test aquarium and/or pond water is to know and understand, as accurately as possible, what is going on in the water both physically and chemically. When problems occur in an aquarium or pond one needs to know as many physical and chemical characteristics of the water as possible.

This information allows the aquarist to better deal with the observed problems. Remember, it is highly unlikely that one can estimate the temperature, salinity, pH, ammonia, nitrite or dissolved oxygen content of the water just by looking at it. Otherwise “normal looking” water can be quite deadly to fishes and invertebrates.

What tests are more or less mandatory?

Remember, both a thermometer and a hydrometer are test instruments. Depending upon the type of pond or aquariums being kept, these instruments are quite valuable and one should have the best of each available.

In addition to the above physical testing instruments one should have (1) pH, (2) total ammonia (NH4+ + NH3), and (3) nitrite (NO2-). These three chemical tests are basic and are the bare essentials. Retailers who sell new aquarium setups without including these three tests as part of the sale are simply leaving money on the table and are doing a great disservice to the customer.

When trying to determine what is wrong in a tank or pond one must perform these three tests as soon as possible. Write down the test results, preferably, in a permanent journal or notebook. Similarly, some tests’ results (e.g. total ammonia) are not completely meaningful unless one also knows the specific gravity, salinity, and temperature of the water being tested. These parameters must also be recorded. Be sure to record the exact test values measured.

What other tests are valuable?

There are numerous other chemical and physical parameters, the knowledge of which, can prove quite valuable. Among these are (1) dissolved oxygen (O2), (2) total available chlorine, (3) total alkalinity (= acid-neutralizing capacity (often, improperly referred to as, “carbonate hardness”)), (4) free and chelated copper (Cu++), (5) nitrate (NO3-), (6) total and calcium (Ca++) hardness. These tests can give an aquarist extremely valuable information about what is going on in an aquarium or pond.

Dissolved oxygen, O2, testing will immediately tell you if the water holds sufficient oxygen for the proper respiration for the fishes and invertebrates. In a pond this test can often help explain why the fishes are stressed at certain times of the day (or night). This can be determined with either chemical methods of physical methods (using a dissolved oxygen meter and specific electrode).

Total available chlorine is very important if one wants to be sure that complete dechlorination has occurred. This is especially important if chlorine bleach has been used in tank or on tank decorations.

By measuring the total alkalinity and the concurrent pH over a period of time in a given system the aquarist can predict when the pH will suddenly drop. Knowing the alkalinity will also help one know how well their biological filtration will perform.

Testing for free and/or chelated copper (depending upon what kind of copper medication may have been used in a given system) is very valuable for determining if enough copper has been added, if too much has been added, and when the copper is safely gone from the water. These tests are very problematical due to the fact that the reagents are very unstable and even the very best quality dry-powder reagents are stable for only about 6 to 9 months.

Testing for nitrate, NO3-, tells one when a new biological filter has been fully “cycled”. However, relying upon the results of nitrate tests as an explanation for catastrophes in an aquarium or pond is not valid. Nitrate is not toxic.

Total and/or calcium hardness are really only important if one is trying to maintain a given hardness and/or calcium concentration. Fishes don’t have physiological mechanisms by which they can tell if the water is hard or soft, and the vast majority of freshwater fishes do equally well in hard water as they do in soft water. In marine aquariums where certain invertebrates and algae tend to rapidly deplete the calcium content of the water it can be very important to test this parameter.

What tests are not really needed and what types of kits should be avoided?

Testing of REDOX (oxidation/reduction potential) requires expensive equipment which must be regularly cleaned and standardized and the information gained is not very meaningful. REDOX electrodes which are continuously immersed in aquarium water develop “memory” as well as overgrowths of epiphytes and bacteria.

Testing for molybdenum, iodide (I-) and strontium (Sr++) in marine water is essentially a waste of time and money. Such testing is available, but not with ordinary colorimetric methods. These tests are simply not reliable.

Tests which use liquid reagents should be avoided. Likewise, some kits which use dry, tableted reagents have been found to be highly inaccurate. Some call these “toy test kits”.

One should use colorimetric kits which make use of flat-sided color comparators instead of round tubes. Also, the color comparison should be side-by-side, with the light basing through both the test chamber and the color standard. The color standards should not be printed on separate paper cards. The best kits actually have the color standard strip immersed, in an adjacent chamber, in the same water that’s being tested.

Don’t assume that electronic, digital test methods are superior to much simpler (and less expensive) colorimetric test methods. A pH meter, for instance, requires daily restandardizing using two different standard buffers. Also, all electrodes (pH, REDOX and dissolved oxygen) require regular cleaning and most must be replaced every 9 to 12 months. Leaving electrodes immersed in the water they are supposed to be monitoring, without regular cleaning, standardizing, and replacement, will produce meaningless readings. For pH, a simple colorimetric test kit is much more reliable and far less expensive.

What about in-store testing for customers?

While this practice builds customer goodwill it is often not very useful. Ammonia, pH, alkalinity, chlorine (and chloramines) and dissolved oxygen readings must be done as soon as the water sample is taken. The time it takes to transport a sample to the store means the sample degrades and the readings are invalid.

What do the different concentration units mean?

This is one of the most confusing aspects of water testing. Ammonia, nitrite and nitrate kits can produce readings based upon the actual substance or ion, others report their values as ammonia-nitrogen, nitrite-nitrogen or nitrate-nitrogen. If a given test kit doesn’t have conversion charts or formulas then be careful in comparing readings from one kit to another.

Alkalinity and hardness kits often report their readings as so many “milligrams as calcium carbonate per liter” (mg CaCO3/L). This is confusing since the two tests and their readings are unrelated. Ask for “The Purple Brochure” for more information on the subject of concentration units.