Water Testing

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Maintaining safe water chemistry levels is critical for trout healthy. Because we recommend that students do all or most of the water testing and maintain data records, water testing also becomes a great learning opportunity as it takes students inside the exciting world of the chemistry that is so important to the wellbeing of our fish.

 

TIC teachers and their students have to be concerned about five chemical compounds: carbonate hardness (KH), pH, ammonia, nitrite, and nitrate.  If the chemistry looks complicated, note that it's more important for the teacher to understand what's going on than it is to teach it all to your students.

 

ABOUT THE COMPOUNDS WE TEST FOR

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pH and Carbonate Hardness (KH)

• pH is a number reflecting the extent to which water in the tank is acidic, alkaline, or neutral. A pH level of 7.0 to 7.6 is desirable. Trout will survive outside this pH range, but high pH increases ammonia toxicity. A lower pH will also cause a slowing down of bacteria reproduction. Below a pH value of 5.5, nitrification ceases. Do not use solutions or additives that are sold to raise or lower pH without consulting a TIC volunteer. These additives mask problems and often result in pH fluctuations that cause fish stress or even mortality.

• KH or carbonate hardness (sometimes called alkalinity) is a measure of carbonate (CO3 2-) and bicarbonate (HCO3-) ion concentrations dissolved in the water. KH levels determine the capacity known as buffering to keep the pH stable. KH is essential to the nitrification process. If adequate KH is not present, the nitrification process will stop due to the loss of all bacteria and cannot be restarted. KH minerals are present in municipal, well, and bottled spring water. The level of carbonate hardness in tap and bottled water depends on the source of the water and the treatment processes it has undergone. Tank water with a low KH level (50 ppm or less) tends to be acidic and can cause rapid pH shifts if not monitored carefully. An initial KH reading of 150 and a maintenance reading of 100 is recommended.

 

Ammonia, Nitrite, and Nitrate

 

To different degrees, excessively high levels of these three compounds are dangerous for trout. Ammonia and nitrite are, without question, the most dangerous. High nitrate levels are not desirable, but fish can often survive them.

 

An ammonia level below 1 ppm is recommended. See the Note with specific information regarding the ammonia test in Chapter 7, Section B, “Maintaining Chemical Balance in the Tank.” Ammonia levels in an aquarium are controlled biologically by nitrifying microorganisms. pH and KH levels are critical to the nitrification process, and to ammonia toxicity. Correct KH levels at the first sign of ammonia increase, adjust pH, and add Nite-out II (nitrifying microorganisms) to deal with ammonia issues. Water changes should be considered a secondary method of correcting ammonia problems.

 

If dramatic increases in ammonia are observed, add Nite-Out II to the tank water to biologically reduce ammonia levels. Water changes may also be needed if the ammonia load becomes consistently too high for the biological filtration to handle, i.e., a level of 2 ppm (not including the ammonium component) or higher. This usually occurs when fish are overfed or there are too many fish in the tank. If the problem occurs frequently, the number of water changes may need to be increased to reduce the daily level of ammonia.

 

THE NITROGEN CYCLE

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If you followed a pre-cycling process, your tank will have fully gone through the nitrogen cycle before you got your eggs. Otherwise, changes in the water chemistry of your tank should conform to the classic nitrogen cycle described below. (Unfortunately, experience has taught us that not all tanks follow the classic patterns.  That's science.  And life.)

 

The classic nitrogen cycle looks like this:

• Readings for ammonia, nitrite, and nitrate are all at zero when you add eggs to the tank. They stay low for a period after your eggs have hatched. (Pre-cycled tanks will typically have somewhat elevated nitrate levels when the eggs arrive.)

• In tanks that have not been pre-cycled, when fish start feeding and producing waste, ammonia rises, but nitrite and nitrate stay low.

• Eventually nitrite begins to rise and, with that, ammonia starts to drop.

• Then nitrate begins to rise, and gradually nitrite goes down. At this point, it is said that your tank “has cycled.” That’s an important milestone. From that point forward, it should be possible to control nitrate levels through periodic partial water changes. (In pre-cycled tanks, nitrate should be the only compound that needs to be managed; ammonia and nitrite should remain at or near zero.)

 

Here’s what the “classic” nitrogen cycle looks like.