This is my 220 gallon with two 5 gallon pools. I created the river rock/sea glass walls in each pool for the crabs to easily climb in and out. They also have craft mesh bridges. Each pool has a large, real coral piece (not living). I have sticks and branches for climbing, lots of bark along the back wall, a large cork round, lots of fake foliage for hiding, moss pits, coco huts, a homemade sea glass hut, and plenty of extra shells.