When buying your first aquarium, go for at least a twenty gallon or bigger if you can afford it. A bigger tank for the beginner makes it easier to have a stable tank in both chemistry and temperature. Trust me; a twenty gallon tank is a lot easier to keep stable than a ten or a five gallon.
The over feeding of fish tends to be a big problem with beginners. I’ve seen food covering the bottom of a tank where it should only be gravel. Feed only enough food that can be eaten in three minutes. Try to feed at the same time everyday. Fish will learn this and they will be at the top of your aquarium waiting for you to get there.
You have to do to routine water changes. A new aquarium, once it has cycled properly, should not have any more than 25% water changed per month. Once a tank is established, you can change 25% every two weeks. Never do a complete water change because all the good bacteria will be removed from the tank and the fish will die.
Before buying fish, check the water requirements and the compatibility with other fish. This takes some planning but very necessary. Not all fish get along and some need different PH levels in the water.
When you have brought fish home, float the unopened bag in your aquarium for at least 20 minutes. Then start scooping water from your aquarium into the bag. This is done to prevent any undue stress on your fish when being introduced to new water.
Keep your aquarium as natural as possible. Do not use chemicals or additives unless you really know what they will do.