Make sure you clean the back of the tank before you glue to it. I use vinegar and then rubbing alcohol. I have fonod out the hard way that if you don't clean it the great stuff will not stick for long. If the tank is new it might not be a problem but if it's a tank that has held water for any period of time there will most likely be a lime scale residue. I like the alcohol because it evaporates very quickly. I know that GE Silcone I was not dangerous to fish in the past, but they may have changed the rescipe so make sure it does not have any mold inhibitors in it as this in ussually arsinic and your frogs will not like that.