Actually, you want a flexible bond. The wood will expand and contract and the flexible glue will allow that without over-stressing the joint. It also acts as a gap filler. The glue has very little to do with structural integrity of the tank. The screws take care of that. The glue is really just a backup. There is so little glue in such a small place that if you solely relied on the glue or relied on it too much, the seams would split.
I've used Gorilla Glue in the past and it is some really nasty and hard to use stuff. Its slick as snot and has a long set up time, so it's hard to get pieces to stay in place while you drill the holes for screws. I don't have large clamps and really never have a need for them, so I wont buy them. I'd never use Gorilla Glue in a project like this. JME.
3/4" birch.