Concrete to bond rock?

[Bryan]

I took the tank down long time ago, so really can't comment much on it long term. I have used the Reef Crest Aqua Weld and it worked not bad for cementing rocks, they have a PRO version, not sure what the difference is.

What works well is drilling a hole in the rock with a masonry bit and insert a acrylic dowel before cementing, adds a lot more support if doing overhangs etc.