The most important thing in your fish's environment is the water. If your fish tank has water that is too hot or cold, too acidic or alkaline, or unbalanced in any other way, your fish could die. In order to properly maintain your tank and keep your fish healthy and happy, you will need to test the tank's water on a regular basis.
You should start by checking the aquarium's temperature with a tank thermometer. It is important to check the temperature of your tank because if the temperature is too high or too low, it can leave your fish vulnerable to disease. Since temperature fluctuations are dangerous to fish, be sure to keep your tank away from any drafty areas, such as windows, doors or heater vents.
The ideal temperature for your tank depends on the kind of fish you have in it so make sure you find out what is ideal for your fish. When you change your tank's water or add new water to your tank when the water level is a bit low, you should make sure the temperature is about the same as the temperature of the water already in the tank. If the water is too hot or too cold, it may shock the fish or even kill them.
pH is a way to measure the acidity of the tank's water. Since pH test kits are inexpensive and it is very important to be sure your tank's levels are right, you should make sure you have a kit on hand for frequent testing. A pH level of 7 is neutral, below 7 is acidic and above 7 is alkaline. Most fish need the pH level to be around 6 or 7. Be aware that anything you add to the tank could change the pH of the water, so always run some tests to make sure the levels are ok after you add new plants, gravel or decorations.
Ammonia test kits are readily available in your local pet store or favorite online pet supply retailer. Ammonia levels are usually measured in parts per million and should always be at zero in a healthy tank. Ammonia in the tank could be fatal for your fish. Make sure you have a biological filter, as it helps prevent ammonia. Cleaning your tank and filter regularly should also prevent ammonia levels from becoming high.
Nitrite and nitrate levels should also be at zero to prevent your fish from dying. These test kits are also readily available and are usually measured in parts per million or milligrams per liter. If you have a biological filter and have high levels, the filter may not work properly. Clean your filter immediately and retest your water.
Finally, you should get a general hardness kit and a carbonate hardness kit. These kits are inexpensive and can be purchased online or at your local store. The hardness of your water depends on the water quality where you live. Most fish like the water to be soft, which is between 50 to 200 parts per million. Hard water is not safe for most fish. Since high carbon can keep pH stable, a carbon hardness kit is important, too.