The volume of that tank is perfect but I am not sure it is 100% fair to keep a 20 inch fish in a 30 inch wide tank, after keeping 12 inch rays in a 34 inch wide (front to back) tank for a year I do not feel this is big enough for such an active bottom dwelling fish....especially when they show breeding activity.
I am going to upgrade to a 48 inch front to back and still I feel these fish need more, after all in the wild they would have oodles more room.
They will live in much less but Would you think it fair to keep an owl in a cage barely big enough for them to spread their wings....I think we need to consider the same sort of argument.