Getting into diy live rock was fun. There are lots of recipes on the web about it as well as lots of discussion on the pros and cons of it. Hours of reading if you are up to it. I did settle on going for it and went with 2 part cement Portland Type 1, 4 parts crushed oyster shell (the chicken stuff from the feed store) and water softener salt (for porosity). I mixed up a batch of the ingredients in a bucket and just dumped it onto a plastic sheet on the basement floor in the shape of a simple pile and let it cure.
After it had set I took it outside and crushed it with a sledge hammer into random chunks. IMO, this provided me with much more natural/random looking rock then I could have made using molds.
I then mounted these chunks to the eggcrate using a 1 to 1 cement/oystershell mix, little on the wet side to get into the eggcrate and the pores of the LR.
Close up of the rock
Back wall is finished. Btw, make sure you eat your Wheaties lifting these 2x4 sheets into the tank, apparently concrete is heavy!
