marbled motoro

Here is a collaboration of some of my rays and tankmates.

I have 3 retics in a 240 gallon tank for now and 2 "mini" marbled motoros in a 75 gallon grow out tank. I feel the 75 gallon is too small for my marbled motors, and I know that retics are very docile stingrays. In the retic tank I also have bala sharks, congo tetras, african brown knifefish...