If you do end up getting a retic, keep it by itself for at least a few months. You are going to have your hands full with just trying to get him to eat. He will need to be fattened up and get comfortable before you think about tankmates. Belive me, it's not easy. No ray is going to be small enough to live in a 75 for life. You should look into a heartier ray (that may get larger since you need to upgrade anyway)for your first. Teacup rays are cheap, but there is a very good chance it will die shortly after aquiring. I've also heard rumors that they are removed from the mother prematurely via c section which kills the mother. Don't know if it is true or not, but if it is, it is not a healthy start to the ray's life and definately not something to support by buying one.