i have a female about 9 inches in total freshwater (250+50 gallon sump.) had her for about 5 months and shes doing awesome, never had any problems with her. Shes more aggressive then all of my other rays. I have not had luck with males though. I got one with her 5 months ago and he would never eat and died about a week later, i recently bought another male and he is yet to eat, had him about 4 days.