I recently for a male motoro stingray, and started noticing a white edge begin to develop. It has been a few day, and I have done water changes. I've checked the water and my ammonia is 0ppm, nitrates and nitries tested as low as possible( I used an api master test kit). I don't know how to treat it because I am new to freshwater stingrays, and I didn't want to use any meds without knowing what would be safe. Any ideas on how to treat it would be great