Ok I have a 55 gal aquarium with rainbow fish mainly. about a week ago I noticed what looked like a piece of string come out of the mouth and anus of one of my rainbows. The tank was due for a cleaning and Life got in the way and I didn't clean it. So once see this I cleaned the tank removing all the gravel and 55% of the water. I also cleaned the entire filter setup I have. I use R/O water with purigen and various sponge/biorock in the filter. I also use Seachem products in the tank. Upon changing the water I used Paraguard, a high dose of brackish salt, prime and stability and neutral regulator when adding back the 30 gal of water I took out. I also quarantined the sick fish and gave it parasite general cure and the fish is still has the "string" hanging out of the mouth. Any thoughts / ideas what else I can do for the sick fish!?? Help? One fish store said I should try to pull the parasite out of the fishes anus and hope the whole thing comes out the "usual path of food" I'm leery of that advice.