What do you use to hold your air stones down? My airstones have a habbit of flying all over the place inside the reservoir. I've thought about plumbers putty, but I'm afraid of the chemicals leaching into the res water. Two sided tape didn't seem to work either. Just curious. Great thread by the way. I just wasted so much time duct taping my res... If only I'd bought a black tub from the get go. LOL.