I have terrible luck with my RD/Midas being with anything else. I have 3 atm that are in their own tanks. They all get along ok until they are big enough to reak havoc on the rest of the tank. I'm thinking about getting rid of 2 of these and getting a barred or amarillo instead.
There is a user on here named: perfect_prefect. He has a large amarillo and could probably answer your questions. Here is a link to one of his threads: