Hi Walter
I am figuring a 5-6" depth, thats with my rock 'caves' a bit more then half buried, two of these in the 29 plus several other pilings of stones to make ledge caves. The other caves are dome shaped rocks molded over round piles of damp sand. It should give a pretty good sized undersand cavern, I actually made them for Tomato clowns. Inside at the base is about 8" dai. Next batch I am making some smaller dia ones, probably 4-5" dia.
I am figuring a 5-6" depth, thats with my rock 'caves' a bit more then half buried, two of these in the 29 plus several other pilings of stones to make ledge caves. The other caves are dome shaped rocks molded over round piles of damp sand. It should give a pretty good sized undersand cavern, I actually made them for Tomato clowns. Inside at the base is about 8" dai. Next batch I am making some smaller dia ones, probably 4-5" dia.