building rock work

[e46er]

How the F do you guys get your rockwork structures to stay together????
Ive tried everything over the 10 years or so Ive been in the hobby and apart from just stacking it in a huge pile it seems to fall apart in 3 months to a year.
Ive always used acrylic rods. tried epoxy, silicone along with them and no matter what they fall apart over time.

of course after they been in the tank for a year I gotta breeak off the corals and pull the rock out let it dry redo it and re cure it. usually leaving my tank looking like crap for a few months.

would pond foam work better? i seem to see mixed reviews online.
HELP!!!!!!!!