Hi james i forgot to answer your question about the steel ties, i connected them together into a loop and put a layer in the cement every 4 inches, and i also bent some for the corners to reinforced the corners a bit more. But i still have to round the corners off with cement as soon as the floor is poured in so that will reinforce even more, and the floor is 50mm celotex insulation topped with 2 layers of chicken wire then around 4inch of concrete. Ive also decided to build a small island which will be hollow which will be nice for the rtc to hide and the island will be a basking area for the musk turtles, i was going to have a flat part on the rock wall for the turtles but i think a small island will look better