that sucks but it would be interesting to know any details to help find out what happend.
when was the last water change and how much ?
how recently were the fx5 put on and what was in them ?
what were you feeding ?
how long you had them ?
im not prying just trying to find some answers that might help other ray keepers avoid similar problems .
sorry for your losses , it sucks when you loose a prized fish , hope you get back into it though and find out what the problem was so you can prevent it happening again
good luck
when was the last water change and how much ?
how recently were the fx5 put on and what was in them ?
what were you feeding ?
how long you had them ?
im not prying just trying to find some answers that might help other ray keepers avoid similar problems .
sorry for your losses , it sucks when you loose a prized fish , hope you get back into it though and find out what the problem was so you can prevent it happening again
good luck