I know of a few people that keep some really amazing mixed species exhibits. One of the most spectacular was an elephant trunk snake, fly river turtle, anoles, and a west african green mambas. It was about 10 feet high by 6 feet wide and three or 4 feet deep and was set up so that the bottom 2' were water for the FRT and such. It was also set up in a way that he could take care of most of the animals without ever opening the cage. If I were rich, I think all of my tanks would be mixed species like his. I will have to dig through my old pics and see if I can find it.