It was the Romans who first collected fish contained in small tanks made of marble. Today, the hobby of keeping tropical fish is popular all over the world, and the variety of fish has expanded over the years. When considering types of fish for a tropical aquarium, freshwater fish are easier and cheaper to maintain than saltwater fish. Most home tropical aquariums are freshwater and range in size from 2 gallons to 180 gallons.
The most popular and easiest to care for tropical fish are livebearers. These are fish that spawn often and bear their young live. These include: the guppy, black molly, red molly and sailfish, all of which have many hybrid varieties.
Many species of tropical fish build nests of small air bubbles. These bubble nests are always built by the male. The nest is made at the water surface among floating plants and is tended by the male after the eggs have been deposited. The most famous of this type is the kissing gourami. Their name comes from the way they pucker their mouths to signal other fish. Another popular nestbuilder is the betta, or Siamese fighting fish. Males will flare out their fins in order to appear more impressive, either to intimidate other rivals or as an act of courtship. Able to breath air, Siamese fighting fish can survive in small aquariums or goldfish bowls.
Another popular group seen in many tropical aquariums are the tetras. Some 20 varieties of tetras include the neon tetra, cardinal tetra, black tetra and bloodfin tetra. The neon and cardinal varieties are very popular because of their small size and brilliant colour. They are a striking sight when swimming in a school.
Known for their pugnacity, cichlids include the aptly named Jack Dempsey, and the Oscar, both of which can grow quite large. The most famous and most collected of this group, though, is the angelfish. Angelfish have been a favourite with hobbyists for many years. They have been crossbred from their original silver and black to about a dozen permutations.
One of the prettiest and most challenging tropical fish to raise is the discus fish. Though in the cichlid family, the docile discus stands alone as the ultimate and most prized freshwater tropical fish species. Discus derive their name from their flat, oval body. The sides of the fish are frequently patterned in shades of green, red, brown and blue. They can grow to about 10 inches in height.