Just get you like a 100-125 gallon. Set it up, let it cycle.. Make sure it is cycled! Get your self a pair of hystrix.. If you can keep them alive, then consider other rays.
the hystrix eventually will need a larger tank, but 18"-24" wide tank will last them a real long time.
Excellent advise. If you can start with a 180 gallon that would be perfect. Used 180's are for sale on creigslist on a regular basis.