Algae eater

• 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 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.

Some freshwater shrimp are also excellent algae eaters:

• Almost all of them belong to the family Atyidae (the only family in the superfamily Atyoidea) including many genera:

• Caridina: red rhinoceros shrimp, bee shrimp, etc... One shrimp well known for its ability to clean an aquarium is the Amano Shrimp.
• Neocaridina: Neocaridina davidi (cherry shrimp), Neocaridina palmata, etc...

• Some of them belong to the genus Palaemonetes (grass shrimp)

Most species of freshwater snails, discounting most adult specimens of species belonging to the family Ampullariidae, which primarily subsist on aquatic plants as adults.

• Surgeon fish or tangs are also known for their appetite for algae.
• Rabbitfish which eat most algae, including cyanobacteria, diatoms, and hair algae.
• Fishes in the suborder blennioidei are blennies.

• Crabs of the genera Mithraculus and Mithrax.

Some snail species such as the Turbo, Astraea, Turban and Nerite snails.[3]