I like the idea of doing this too. I have one laying around, believe me, it's not in use. It could easily be turned into a reactor. Remove the tube as previously discussed. If it's stuck, it could be cut out. Fabricate a few plates to go in it out of acrylic. The hard part would be the top. If I left it freestanding in my sump, it would be well over the water level and would cause splashing. I need some ideas for an outlet. Could just cut the entire top off just like Dragracer drew. I think that's the best solution i just like drawn earlier in the post. I'll try to do that this weekend and see how that works out.