Don't glue them ALL together, think about when you want to remove them.
I'd make sure there is space between the glass and the rock to prevent "dead spots".
Have you thought about adding some good quality LR
to help "revive" the marco? The rockscape looks nice, but not very natural. I would try finding LR
with some different shapes and create some shelves (low, middle, and high); you have to think about the future and where the corals will go.
So far it looks good, keep up the "cave" idea for the fish, but don't forget about the corals!