However, their average size in most aquariums tends to be closer to 6 inches (15 centimeters). They typically reach these larger lengths when kept in optimal conditions over many years and in larger aquarium setups that mimic their natural surroundings well. The Butterfly plecostomus has a relatively rapid growth rate compared to some other pleco species but should generally not be expected to become too large too quickly in home aquariums when appropriately cared for.