Last month we looked at some of the individual characteristics that determine the quality of water. We reviewed the critical factors, those which will result in the death of your fish if they are not kept within a specific range. These critical factors included Ammonia, Nitrite and Dissolved Oxygen. This month we'll conclude our article by looking at the non-critical factors. Let's begin...
pH refers to the relative concentration of acids in water. A value of 7.0 is considered neutral - less than 7.0 is acidic and more that 7.0 is alkaline. Acids are produced naturally in the aquarium as a by product of the nitrogen cycle, as well as other processes. Over time these acids will tend to drive the pH down. As a non-critical factor, fish will tolerate a wide range of pH conditions but the extremes must be avoided.
Alkalinity is a measure of the buffering ability of water - the capacity of water to accept acids (as discussed above) without causing a drop in its' pH. The higher the alkalinity the greater the water's ability to prevent rapid swings in pH. If you're having difficulty maintaining a constant pH level, or are not able to lower your pH, be sure to check your alkalinity.
Total Hardness is the sum of calcium and magnesium in water. Water hardness is only relevant to freshwater aquariums and is generally not a concern, unless the water hardness is at one extreme and the fish you want to keep prefer water at the other extreme. Total Hardness should be maintained in the range 0 - 200 milligrams per liter (mg/L). Hardness can be lowered by using peat or ion exchange resins. To increase hardness you can add calcium and magnesium.
Nitrate (not to be confused with nitrite) is the end product of nitrification. Generally nitrate will accumulate in all aquariums but as a non-critical water quality factor it is usually not a problem. It is not uncommon to see nitrate levels of several hundred milligrams in aquariums but nitrate should be maintained at levels below 50 mg/L. Nitrate is reduced through water changes and the use of live plants.
While there are a number of other water quality characteristics that can come into play, these and the ones we discussed last month, are the most relevant to the aquarist. Maintaining good water quality is important to your fishes health and requires diligence and observation. A regular schedule of testing both the critical and non-critical water quality characteristics should be established. Things that can change the water quality include evaporation (only the water evaporates, the salts are left behind), nitrification (as we previously discussed) and overcrowding or overfeeding.
While I encourage everyone to test their water, I also caution against becoming to fanatical about reaching and maintaining a certain water quality. The goal should be stability. Most fish can adapt to a wide range of values, but they will seldom tolerate sudden changes. Therefore, maintaining a consistent, stable aquatic environment should be the goal of every aquarist.
Dan Cole
