Parrot Cichlids are considered to be large-bodied cichlids. As such, they require oversize filters and large amounts of water to dilute the growth-stunting, life-shortening secretions and toxins that build up between weekly water changes. With insufficient dilution, these chemicals and compounds quickly and adversely impact the health of the animal.
30-gallon aquariums are thought by most enthusiasts to be the absolute smallest size that a Parrot Cichlid can be housed in, with an additional 10 gallons per additional fish. More water is always better, and by exceeding this standard the aquarist allows for territories to be formed, which can only enhance the well-being of a Parrot Cichlid. More water also permits the inclusion of schools of bottom feeding and dithering fish.
Don’t believe anyone who tells you that a Parrot Cichlid can be safely housed in a 5 or 10 or even a 20-gallon aquarium with a single, small filter. It simply isn’t true.