Securing 1/2" pvc inside dry rock?

[lastlight]

I'm drilling holes in my dry rock and using 1/2" pvc to peg things together. What can i use to keep the pvc from coming out? I'd prefer something I can buy at HD but if I should use the tubes of the green/white epoxy for reefs then please advise where it is best priced...

Another thing that concerns me is not just stopping the tube from wiggling...but from pulling out. Should I drill holes in the tips of the tubes and try and force my bonding agent into them as well?

Thanks for any advice.