Most tap water contains chlorine and ammonia that can kill your fish. Ask your fish dealer if you need an additive in your area to neutralize these toxins.
Overfeeding is one of the most harmful and common errors in caring for fish. The food not eaten turns into toxins in the tank. Feed your fish small amounts of food once or twice a day. If they eat the food in two to three minutes and start looking for more, add another small pinch.
Some species, such as goldfish, thrive in unheated water, but most fish need a water temperature of 70 to 78 degrees.
Some fish are very hardy and relatively easy to keep, while others are so fragile that a temperature drop of a few degrees will kill them. Choose fish for your tank that all require the same environmental conditions.
Keep your tank out of direct sunlight or near a heating or cooling source to avoid algae growth and prevent the temperature from changing.
Fish constantly add waste and toxins to the tank, so filters, especially an under gravel filter, is important to keep the water clear and safe.
Once a month, with a parent supervising, remove about one-third of the tank water. Replace it with treated tap water at the same temperature.