I have a 3ft x 4 ft rubber cement tub above a 600-gallon fish tank with some of the return water from my ultima filter rigged to fill it 1/4 to 1/2 inch full and drain back into the fish tank with constant water flow. I use 12 one gallon grow bags with potting mix and organic fertilizer mixed on the top half, so it doesn't leach out. The fabric bags wick water up and keeps the top half moist. I also fill clay pebbles around the bottom of the grow bags to prevent algae growth.
I have a constant supply of leafy greens growing in the tub year-round.
It's easier to maintain than the Kratky method, since the bags have enough organic fertilizer to see the plants through to harvest. In addition, cherry tomatoes can also be grown in the one-gallon bags, but the fruits aren't as large as the ones grown in larger containers.
I have a bigger 3 ft x 8 ft x 8-inch-deep plastic grow bed above a 1,000-gallon fish tank that is set up almost the same way, but I keep the water level higher, and I use a bell siphon with a small hole on top to prevent the siphon from triggering, so the water drains from the bottom and not the top. I need the water to drain from the bottom to prevent my duck weed from draining out.
I use the duck weed as a food supplement for my White Nile Tilapia's. White Nile Tilapia's can grow up to 10lbs and they look and taste like saltwater fish to me.
View attachment 3653107