Monitoring and Maintaining Water Quality
The greatest cause of aquarium fish deaths is poor water quality. High levels of ammonia, nitrite, and nitrate, as well as extreme pH levels can overstress a fish’s system. Therefore, you will need to closely monitor and maintain the quality of the water in your aquarium, especially as you increase the number of fish.
The most accurate way to monitor your water quality is to purchase the proper fish tank equipment. A heater and a thermometer will keep the water at an appropriate level (often between seventy-five and eighty degrees, but it varies with each species).
A filter keeps chemicals at appropriate levels (though you will need to regularly change the filter cartridge) and a chemical test kit will tell you if any chemicals are at abnormal levels. In general, all chemical levels should be close to zero, with the exception of alkalinity (120-300 mg/L) and pH (approximately seven).
You may also hear about aquarium cycling, a term which refers to the nitrogen cycle operating within your aquarium. When you add fish to your fish tank, nitrite and ammonia levels will rise, so, as a general rule, wait until those levels return to zero before you add more fish.
If you have a saltwater aquarium, maintain a salinity level between 1.020 and 1.025. As water evaporates, the salinity in your tank will increase, so you will need to occasionally add freshwater.
Finally, it is very important to regularly change some of the water in your aquarium. Estimates vary on the exact amount you should change, but it’s a good idea to change approximately twenty-five percent of the water in your tank every two weeks.
Unplug any electric appliances, such as your filter, remove water using a cup or small bucket, and then use dechlorinated water to refill the tank.