Algae eater, also called an algivore, is a common name for many bottom-dwelling or algae-eating species that feed on algae. Algae eaters are important for the fishkeeping hobby and many are commonly kept by hobbyists.

Freshwater

Fish

Some of the common and most popular freshwater algae eaters in aquariums include:

• Many loricariid catfish of South America, such as genera Otocinclus, Ancistrus, and Plecostomus, constantly graze algae and biofilm, although many species of “plecos”, which attain an adult length of over 10 inches, eat much less frequently as they near adulthood.
• The Siamese algae eater, Crossocheilus oblongus, is a more gregarious and tolerant cyprinid that ranges up to 15 cm. It is one of the only fish that will graze on “black brush algae” (freshwater Rhodophyta, or red algae), but even so will eat anything else in preference.
• Fishes of the genus Gyrinocheilus, family Gyrinocheilidae. There are three species in this genus with the Chinese algae eater, Gyrinocheilus aymonieri, the most common. Small specimens make good community fish but may become territorial when older.
• American-flag fish, Jordanella floridae, are also dependable algae-eating fish. They are one of the only fish to graze on black brush algae, as with the siamese algae eater, and will also indiscriminately graze on other algae such as diatoms and hair algae. However, like all pupfish, they can be nippy to fish smaller or slower than them. Males can also be territorial.

Saltwater

Some of the known types of fish to eat algae are Blennies and Tangs, but along with fish there are snails, crabs, and sea urchins who also eat algae. These species are known to eat red slime algae, green film algae, hair algae, diatoms, cyanobacteria, brown film algae, detritus, and microalgae.