Here are some of the most popular freshwater fish species that are commonly kept in aquariums, each with unique characteristics and care requirements.
A common rule of thumb for how many freshwater fish you can keep in an aquarium is to allow about 1 inch of fish per gallon of water; however, this can vary depending on the specific fish species, their adult size, activity level, and bioload, with heavily planted or densely stocked tanks often needing more filtration and swimming room.
Overview The Red-bellied Piranha (Pygocentrus nattereri) is the most famous piranha, silver with a red belly. Found through much of the Amazon basin, plus the Essequibo and the Paraná–Paraguay system. Grows to about 14 in (35 cm) standard length. Illegal to own in...