smaller rays (retic's) need 72x30x24 as a minimum, for medium rays like motoro, leopoldi, p14 you need 96x30x24 for a pair or 3 fish. Totally intolerant of ammonia & nitrite, need huge filtration.... my ray tanks has a 75 gal sump and 2 large canisters...... for flower/tiger etc you really need a pond. High protein diet...shrimp, fish etc mine eat about £3.oo a day....just for the rays.
top predator, so only with relatively large & peaceful to moderately aggressive fish
fantastic animals... but not cheap to set up or keep.