Single Fish In Community Tank With Ich

I have a 20 gallon community tank. I introduced a new swordtail. After 3 days I noticed three ich spots on her pectoral fin. I removed her and treated her in my hospital tank with heat and rid ich. The spots disappeared after 5 days. I waited another 2 days then introduced her back into my tank. Three days later I notice another couple of spots on her fin. None of my other fish have shown any signs of ich since her first signs which was over a week ago. All my other fish have been healthy and happy in a stable tank for 3 months. I'm afraid to treat the tank because it has been so stable and no signs of ich ever except on her. Should I remove her and treat again separately or treat the tank. My thinking is that if I remove her to treat and none of my community tank fish develop ich after a week then the parasite would be gone

 

No - you need to treat the whole tank. If they are on one fish they are also in the gravel & water. There is a method of treating with heat which would eliminate your need for medications. I will try to find the link. It would help you to learn about the ICH life cycle so you know why a week of the visibly sick fish out of the tank is insufficient. ICH is frustrating, but hopefully with more info you will be able to successfully treat it.

ICH (ICK) Life Cycle and Natural Treatment
ICH (ICK) Life Cycle and Natural Treatment

 

As I understand it the entire life cycle for ich is 7 days (at my tank's water temp) from trophont to tomont to theronts. If the theronts don't find a fish host within 48 hours they die. If my other fish don't show signs of ich in, let's say, two weeks then can't I assume that they didn't get infected? And if not, haven't the theronts died? Or is it possible that the trophonts on this fish never had a chance to fall off because I caught it immediately and removed her

 

So, I was wrong. While treating my Swordtail for ich in a separate tank, I noticed 2 spots on one of my tetras fins and 1 spot on a fry platy. I have been treating there community tank with Paraguard and heat. No visible signs for 3 days in either the community tank or my hospital tank. Fingers crossed I've got it licked.

 

Good - but regardless of the visible signs of ICH disappearing please complete the full course of treatment.