Both of my stingrays are moving back and forth vigorously on the crushed coral substrate. It appears as if they are scratching, as if they have an internal parasite, should I be alarmed of is this nothing? And if so, what should I treat the stingrays with? I live in Thailand so brands or types of medication which are common in the U.S. do not exist here and are known under different names. Could anyone please recommend a parasite which may be attacking them or a recommended treatment?