Most pet stores and libraries have good reference materials. Learn about the animals you wish to have. Carefully consider the largest size an animal will grow before you purchase it for your home aquarium. While Sea World is capable of taking care of large fish such as nurse sharks, they probably should not be purchased for most home aquariums. Make sure that food for the species you wish to have is consistently available.
Some fish feed only on corals.
These fish are difficult to keep in home aquariums because there is no commercial food supply available for them. Be careful to purchase animals that are compatible and that will be able to live together in the size aquarium you have. Ask your supplier to check water from your aquarium before you purchase animals. If your supplier is unable to test the water for you ask him for advice on the correct parameters of pH, ammonia, nitrates, etc. Regularly test your aquarium water.