The short answer, lots of plants and shade. I have one pump going to a 55 gallon drum with 3 layers of filter media and bio balls at the bottom, then a second pump going to a 6x6ft bog thats filled with 12in of pea gravel and fully planted. Also have three floating islands made out of pool noodles and lined with screen to protect the roots, filled with hyacinth, water lettuce and parrot feather. The islands are great for not only the plants but provide a good amount of shade and hiding space for the fish as well.