Securing corals with epoxy or other methods

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My corals keep getting knocked over by my various crabs and turbo snails.

I have two montipora digitata frags which I epoxied onto round plugs and set the plugs on the rockwork. However they kept on getting knocked over. I've tried to epoxy the plugs to the rockwork but it won't stick. I am using super-glue gel, it doesn't seem to want to set well under water.

I also have several LPS corals which have been knocked over and they didn't attach well to the rocks with epoxy either.

Any suggestions, alternate epoxy products or other ways of fixing my corals in place?