Epoxy question

[polarbear]

So awhile back I had posted a thread asking what I could use to hold some acrylic squares to the back glass of my aquarium. I had a great idea to mount my monti caps which worked for about a month but then they feel off. I used super glue gel but I guess it spread to thin between the pieces. Is there something else I can use that will cure under water? Maybe a 2 part epoxy.

[Big_Pun]

not to glass it's too smooth do you have a over flow box? not enough texture for it to stick to.
my old tank
http://img.tapatalk.com/d/14/03/24/zede5y7a.jpghttp://img.tapatalk.com/d/14/03/24/myru8agu.jpg

[polarbear]

I do have an over flow but I have 5 different monti caps to attach and not enough room on that one overflow. I would hate to get rid of these. I've had them for a long time.