How to build a reef safe 3D background?

[kuzzyphuzzy]

Hey everyone!

I am currently interested in putting together a 31 gallon AIO reef tank and building a custom background for it. The idea I have in mind is to almost make the tank look like it’s up against a drop off or slope on a coral reef. I have tons of fragments of live rock that I’m interested in molding together to form rock wall.

I was able to get my hands on some of that Marco reef cement you can buy at the LFS, but I don’t know if it is going to hold up well as a mortar. I actually made a near complete background already out of great stuff(pond annd stone) and sillicone. But I have since learned that even though it’s made for water, it will begin to fall apart if underwater for too long.

Any suggestion for a reef safe mortar to help form this background? I’ve seen some people use sand grouts and other materials. But I have yet to find anything that really says that any kind of mortar from a hardware store is going to be safe…

At the bottom here is my “rough draft” version that used the great stuff. Since I can no longer really use it. I plan on going back and getting as of the coral as I can to try again

 

[exnisstech]

I've used e Marco 400 to build structures and have not had any issues after more than two years in the tank.

 

[likemike99]

the marco mortar is great as long as you don't make it too thin. I recently made these with marco mortar