The world as we know it is in balance. Animals breathe in oxygen and give off carbon dioxide. Plant absorbs carbon dioxide and give off oxygen as part of there process of photosynthesis. Animals eat plants and animals wastes, feed plants. Water evaporated from the seas and come back to freshen the earth.
The absolute balance of an aquarium world is not usually possible for a beginner. Usually the fish give off more waste matter (both in gas and solids) than the plant life can absorb. And plants almost never provide sufficient food for fish life in an aquarium tank (the things that the aquarium keeper must provide to maintain plant life). But too much encourages the excess growth of algae, causing green water and green-coated tank walls.
Below are the 4 things you as an aquarium keeper must learn to balance:
Food: It must be a balance of vegetable and animal matter. The reason is that insufficient food stunts the growth and lowers the resistance of fish to disease. On the flip side too much food can also harm the fish by polluting the aquarium.
Size of tank: The tank must be larger enough to provide space according to the number and size of the fish. It mustalso have sufficient surface so that oxygen can be absorbed to satisfy them.
Temperature: This poses no problem for us in this part of the world as the range of 24 degree centigrade to 30 obtainable here is most ideal for tropical fish.
Gravel: One or two inches of sand gravel is all that is required to anchor plants. However be carefull because too much gravel accumulates waste matter that tends to pollute the aquarium.
Master balancing these 4 elements of your aquarium and your tank will look great and your fish will live a long happy life!