The kids are 3 and 6, well almost 4 and 7 in july.
The back of the tank is light diffuser, with concrete, oyster shells, and aragonite and pvc. it was made in several smaller pieces to be ale to fit through the top openings. The main roacks are tufa rock with spray foam coated with aragonite. Had another one on the left side but it floated so I took it out and cut a bunch of foam off. Just need to epoxy it again.