Pretty soon I will be getting a new tank. The demensions will be 6'x4'x2'. The rays I have right now are a 5in riticulata and I will soon be getting a pair of motoros about 9in and 10in. Given their adult sizes would I be able, in the future be able to add another ray to this tank or would it be pretty much full. It will just be these 3 rays for now, no other fish, unless I can add another ray. If I could add another ray what would you guys suggest to add. Something different than what I already have.