Bottom feeders tend to stay at the bottom or sides of a fish tank. They eat algae, bacteria and any fish food left uneaten by the other fish. There is a popular misconception that they eat fish faeces, but they do not, according to "Freshwater Aquariums for Dummies." Bottom feeders play a helpful part in maintaining a good chemical balance in aquarium water. They also are fascinating to watch.
These are the most common bottom feeders sold for fish tanks, as they only grow to be 6 inches long or less. The smallest pet species is the Otocinclus algae eater, which only grows to 2.5 inches long, but needs to be kept in schools of three or more. Other popular pet species include the Siamese algae eater or Crossocheilus siamensis and the Chinese algae eater, also called the sucking loach or Gyrinocheilus aymonieri. Algae eaters have slim, streamlined bodies, flat pale bellies and sucker mouths. They need supplemental feeding with commercially prepared algae wafers, as a fish tank cannot produce enough algae to feed them.
They are also known as plecos or suckermouth catfish. There are many plecostomus species, many originally from South America. The have a sharp barb on their dorsal fin which can stab if the fish is bothered. Plecos also need to be fed algae wafers and occasional blanched vegetables like green beans or peas. Plecos tend to hide during the day and come out at night. The common plecostomus, or Hypostamus plecostumus, can grow to be 2 feet long. The large adults can survive in koi ponds and often with large, aggressive fish like cichlids.
Loaches look like small catfish. Some species, like the clown loach or Botia macracantha, are brightly coloured with black and orange bands. Loaches originally came from Asia and India and, like plecostomus, are also nocturnal. Loaches are strictly carnivorous and will ignore algae but are excellent at picking up any food ignored by other fish. Loaches can become aggressive with other fish unless they are kept in small groups of three to five, according to "Freshwater Aquariums for Dummies."
This is the common name for corydoras catfish, which are omnivorous and tend to grow less than 3 inches long. They also need to be kept in groups of at least three, although they are nonaggressive toward other species. More than 50 species of corys are available for home aquariums, but the most common species are the blackfin cory (Corydoras leucomelas), the bronze cory (Corydoras aeneus), the panda cory (Corydoras panda) and the 1-inch long pygmy cory (Corydoras pygmy).