[garuf]

I would suggest reading up on how to look up on the fish on Monsterfish keepers and other specialst forums. I read a lot into it when my uncle started breeding motoro's and if a 40 years of experience fishkeeper struggles a noob will almost certainly too.
They're extremely difficult to keep, they're VERY rare in the wild, they're expensive to keep and look after as well as producing about as much waste as mabuna if not more with being cariverous. Your tank is too small, the style of tank aren't really suitable and you're already at the top end of stocking and with a lot of unsuitable tank mates, my advice would be to forget rays for this tank. Even the smaller hymachura asiatic rays aren't really suitable.

 

[garuf]

BTW, a lot of Uk ray breeders use shallow wide tanks with nothing smaller than 120gallons. They're also extremely sensetive to ammonia and nitrate. Don't buy cheap, it's a bad move as it will encourage shop owners to persue more cheap imports, buy tank bred stock from a recognised breeder and not put further pressure on sensitive wild stock, yes it's more expensive but quality of stock and their wellfare should be your paramount concern with such sensitive animals.