I don't know if that would cause problems or not. I have thought the same thing multiple times though. I have 2 300g Rubber maid stock tanks doing nothing right now too. I had them as part of my salt set up a long time ago. Thought about it then too. Maybe we should try it. I thought I'd just cut out a section from the side and leave the top rim intact. Then get a nice thick piece of acrylic and try to bend it to the same shape, drill hole and silicone and bolt it in place. Mine are round I know some of the smaller ones are oblong. The window frame is a good idea too