I wouldn't use anything in a tank except for aquarium silicon. That's what holds aquariums together. You can get it at pet stores in the fish section.
Have you considered using magnets to hold up a dock? Industrial girl 2000 first suggested this. I use magnets and they work well. Here's a link to the thread on the subject:
Posted: Sat Feb 23, 2008 6:09 pm Mighty putty
