I had no problem with the combo but I had to spot feed the goby as he wasn't fast enough to beat the rays to the food. I got bored of the goby and traded him as they are nocturnal and never cruise the tank. Mine did a good impression of a piece of driftwood.
mine is awesome. He comes up to feed by hand if he's not getting enough! He's out & about all the time. I think I'll try it. Thanks! How about a red tail/tiger shovelnose cat with a stingray?