My 1st Home Test Aquaponics set up. 25 gallon gravel grow bed serves as a bio-filter for the fish tank. The fish tank is approximately 50 gallons so it wold accommodate a second grow bed. I'm planting directly in the gravel as well as in soil filled trays. The trays have mesh bottoms to allow roots to grow into the gravel filled grow beds. An aquarium air pump provides additional O2. I plan a 20% water exchange each week.