A new aquarium owner should stick to species that are hardy, peaceful, and easy to feed. Fish that meet these criteria include danios, platies, swordfish, neon tetras, cory cats, dwarf gouramis and catfish of the genus Plecostomus.
Before buying fish, test the water for pH and hardness and decide whether or not the tank will be heated. Danios can tolerate unheated aquariums, while most other species of tropical fish need a heater. Live-bearing fish, such as platies, Plecostomus catfish and swordfish prefer harder water with higher alkalinity. Neon tetras, cory cats and dwarf gouramis prefer more acidic, softer water. Bettas and angelfish are also easy to keep, but male bettas will fight if left in the same tank, and angelfish can become territorial when they mature.