Aquarists new to keeping an aquarium may be tempted to add fish that eat poop as part of their ecosystem, thinking this will keep their tank clean. Unfortunately, while certain fish do consume waste in nature, this behavior should never be replicated within an aquarium environment and could actually endanger both its inhabitants as well as water quality in general.
Fish That Eat Poop
Many popular pleco and tilapia species in aquariums have a reputation of eating their own waste, often including plecos and tilapia. Scavenger fish such as plecos and tilapia have been observed eating waste products as they try to feed themselves; this behavior should not be encouraged, however; eating too much waste signals malnourishment in aquariums; the more fish consume poop than live food and potentially die without ever receiving proper nourishment from live food feeding stations!
Wild fish typically rely on algae to meet their nutritional needs; however, given its poor source of micronutrients, many also eat feces from plankton-eating fish in order to get these essential micronutrients. According to Hannah Rempel of the University of Texas Marine Science Institute's researchers, 85-87% of plankton eaters' waste was eaten by parrotfishes and surgeonfishes!
Though these fish eat their poop in the wild, they cannot be considered coprophagous (fish that consume human waste). Instead, they take pleasure in digesting it as food for both themselves and the microbes within an ecosystem; when decay occurs it provides vital nitrogen-rich compounds which help support life forms within that particular environment.