Sure do, been keeping rays for 17.5 years consistantly. Been breeding them for 9 years. Currenlty have over 100 adult rays in my breeding program.
Some species of ray at a small size can be a little hard to tell, just have to look very well.
Best way is to try to get them up against the glass if you can. If not bag them up and hold em up and look that way.
Smaller rays ( pups ) claspers ( males ) will be very very small. The claspers are located at the base of the tail on the underside in between the " flag fins ( caud. fins. ).
Hope this helps, Tfd.