OK new question - feeding off the other thread I had posted about the filtration question - you mentioned hydroton as a growing medium for the plants. If I were to use this, any idea how I'd keep it elevated so that it was just in the top of the 100 gal stock tank? I'll be using eggcrate to hold the filter sponges above the pvc intake pipes, but obviously the hydroton would fall through that if I put that overtop of the sponges. Would something like window-screen material overtop of the eggcrate work? If so, any thoughts on the best way to attach it? If not, any suggestions on what might work? Ideally I'd like something that the plants could grow though if they decide the current isn't too strong. I would think window-screen might be too tight of a weave for that though... but I can't think of anything else that might work at the moment. Suggestions?