The water in your tropical aquarium is more than just hydrogen and oxygen — there is a lot of other stuff going on in your tank. Understanding some basics will help you provide a safe and healthy environment for your fish.
There are two types of bacteria that may live in your tank: aerobic and anaerobic. The aerobic kind of bacteria needs oxygen to live. The anaerobic kind of bacteria can live without (or just does not need) oxygen.
You will want to invest in an aquarium testing kit (or separate kits to test for separate things) that checks for ammonia, nitrite, nitrate, pH, water hardness, and chlorine.
- Ammonia is a chemical that results from two things: fish waste and decomposing food in the aquarium. Too much ammonia can kill your fish! Ideally, you’d like the ammonia level in your tank to be zero.
- Chlorine is a chemical found in most tap water — it is used to kill bad bacteria in drinking water. However, it also kills fish. You want the chlorine level in your tank to be at zero. Chloramine is a combination of chlorine and ammonia that is stronger than chlorine alone, and it too can be deadly in your tank.
- Copper can come in with your tap water if you have older copper pipes or use copper-based medications. This metal can be dangerous (even deadly) to fish and invertebrates.
- Nitrite and Nitrate — these are both converted ammonia. Bacteria in your tank convert ammonia first to nitrites and then to nitrates. Nitrites are just as toxic to fish as ammonia itself. Nitrates are not as toxic, but can be harmful in high levels. Your tank nitrite levels should be zero and your nitrate levels should be less than 20 parts per million in freshwater tanks.
- pH is a measure of the acidity or alkalinity of water. A measure of 0 means very acidic water. A measure of 14 means very alkaline water. A measure of 7 is neutral.
- Phosphates can come in with your tap water, from dead plants, and in fish food. High phosphate levels can lead to algae outbreaks, but keeping up with aquarium maintenance and performing regular water changes can help keep phosphates (and algae) out of your tank.
- Salinity is the amount of dissolved salts in the water. Specific gravity is a measure of the density of dissolved salts in salt water as compared to fresh water.
- Water hardness deals with the amount of minerals dissolved in the water. Calcium and magnesium are two of the more common minerals you will find in tap water. Soft water has relatively few dissolved minerals; hard water has many. If your water is too soft, you may have trouble maintaining pH levels.