They are kept right now in a plywood pond with a pond liner. It was originally a Savannah Monitor cage, built to hold litterally 2 tons of dirt. Nothing fancy, but it works. The dimensions are 8'x4'x2', roughly 475g.
I have 2 diy bucket filters (Wendy filter) running, one with a mag drive 7 pond pump, and the other with a pond pump rated at 500gph from my local box store.
I do weekly water changes and replace 70%-80% of the water. I have been expirimenting with a method to introduce tannin rich water to the setup, using peat moss and a 96g trash can. I'm not so concerned with the pH (fortunately my tap water is already acidic), but more with the benefits of the black water. I literally make tea with the peat moss, hot tap water, and weed blocker. So almost 1/3 of the water that i change is the tea.
Mazuri Crocodile chow (formulated for crocodilians, larger turtles, and lizards) is what I use to supplement some of the missing nutrients they would normally get from gut content, and other organs that are removed from the frozen fish I feed. These guys usually only consume whole prey items and obsorb all the calcium and minerals they need from them. Some of that is stripped from being frozen, and processed for human consumption.