Bunching onions, a squash, and watercress for now. The tanks have fish and the water gets passed though the gravel grow bed which filters the water and gives a place for bacteria to grow and thrive which keeps the water clean for the fish. The plants consume any nitrates left over after the bacteria do their job and everyone wins!
You can do this on a small scale with a 20 gallon on a counter and do herbs for a kitchen to start. You can have both a really nice looking aquarium and free fresh herbs!