Research on an aquaponic system rearing common carp and mint suggests that the ratio 1:2 (fish: plant) showed optimum fish production, plant growth as well as nutrient removal. you have to determine the ratio for your aquaponics system based on several choices you have made as listed above in the post.. For the eco-cycle 20 gallon system, the ideal number fish will also vary, but here are some good targets: small tropical fish (tetras, guppies, platies, rasboras, small gouramis. etc.) – 30 inches of fish medium tropical fish (peaceful cichlids, catfish, mollies, medium gouramis, etc.) – 20 inches of fish goldfish – 15 inches of fish these target fish populations are best built up incrementally..
