I set this system up in our kitchen last year to help hone my skills of growing lettuce and herbs using a 50 gal reservoir with the plans of switching to a 50 gal fish tank this year. Just getting ready now make that move, and trying to figure out what kind of filtering system would be best. I used coco 3" cups in the gutters when doing "hydroponics" and I am wondering if I should switch to the clay in the gutters and add earthworms. Am I barking up the wrong tree? Any advice out there? Also wondering what kind of fish I can do in that size tank. It is my hope to get the basic skills with the balancing between fish and plants and then go to something bigger and on a more commercial level. We sure enjoyed our butternut lettuce all last winter and can hardly wait to have the aquarium right there in the kitchen!!