Grow an arowana out in it for 5 months or so and then put them both in the 230. If you do have mates for stingrays make sure they don't eat all the ray's food.
It would probably work because the salvini would be the dominate fish and keep them in line. The tank is big enough so there might not be any problems at all, accept for maybe the salvini they can get very agressive.
I have a male dovii in a 110 a pair of jags that havent quite bred yet in a 125 and mixed CA/SA tank thats a 75 all the fish are juvies right now. I'd post pics but I don't have a camera.