i dont know if this is the correct, or smart way to do this, but i had a potential problem of flukes with one of my male leopoldi rays, and in there i had 2 retic rays as well that would only eat earthworms. i dosed the tank with a double dose of prazi pro (spreading out the dosage every half hour so as not to shock, and upping my water change frequency) upon the advice of an experienced ray keeper on this forum. prazi pro is known to highly increase the appetite of fish. the day after I dosed the tank both the retic rays started eating the shrimp, worms, and i think pellets that i dropped in there to feed the other fish like it was magic. again not sure if this is the smartest way to go about it, i heard various opinions on prazipro killing your bio filter and crashing your ph, and medication is imo never the smart idea if you dont need it, however if youre stuck maybe you want to give it a try, as the experienced ray keeper that advised me to try to treat for flukes says he doses prazi pro twice a year just to keep all his rays healthy regardless if theres problems or not.