Crayfish parasite/fungus?? PLEASE HELP!!!!!!

Does anyone know of any crustacean friendly parasite remedy's?? i have lost one red cray, trying to save the second. It has a strange bristle like growth about a quarter of an inch long thats white/ dark brown growing out between his rear legs. I have started with a 10 ppt salt dip for an hour but was hoping to follow up with some low level medication but can't seem to find anything that is safe for crustaceans. Any help would be awesome as i can't find much on the web reguarding crayfish. ph is 7 to 7.5, nitrites - 0, nitrates - 20, gh-180, kh - 120