I would agree with the parasite.. With rays, unless the problem becomes 'out of control', I use a safer, all-natural method in garlic extract. I have found it to be much cheaper if you buy it from a nutrition store as well, rather then a commercial aquarium product.. I use a syringe to inject earthworms with it.. If it dosn't seem to be working (monitor the feces they are producing, it should be long single strings, no poop or little poop usually isn't a good sign), then I try Metrodazinole, however DW suggests Praziquantel. Either way, I have never killed a ray from meds, nor have I ever done a full dose. I always 'soak' the food in the med I am using..
