interesting designs. The first thing I ever tried to make was using hydraulic cement and chicken wire. I fashioned a rectangular pipe. with an door on one side, where I folded the door in which cut the pipe tunnel into 2 halves. I was able to stack my creations into a wall, or create new nesting sites for my fish. You should watch Tank kings, they create fake coral inserts. Oh, try not to create any unlit portion on your pieces, corals will have a hard time growing downwards though that.