Just my two cents, but if any of your fish get Ich ever again and they are less than $40, not rare, and you don't have a quarantine tank, I would git rid of the fish. Since you have a 90 gallon I wouldn't want to risk the rest of my tank to Ich and the NO-ICH stuff is extremely expensive. As for now, I would treat the pest cycle for a couple of weeks just to be safe, but if this ever happens again in the future you can bring the fish to an LFS and see if they would take it for free and have them deal with the Ich since you gave them the fish for free. Not to put everything off on them, but since you'd be giving it to them for free I think it would be a fair deal. If you can't do that, then I've heard you can cup the fish out in water and put it in the freezer and it will slowly stop its heart rate without it having to go through pain. And since you don't spend a fortune on the NO-ICH you can buy another fish to replace it if you wanted to and you won't have to buy multiple large bottles of the NO-ICH. Again, this is just my opinion. The only time I've had to freeze a fish was when I had a pregnant guppy in my old fresh water tank and you could tell she was about to die... she had given birth every single month for about 6 months and her last batch had been 132 babies. I'm assuming if she had lived there would be about 200+ babies. The other time I had to freeze a fish was when I got one about a year ago and I came home one night and found it still breathing, but lying on its side and it looked like it was dying so I spared it the pain of dieing and froze it. If you ever get Ich again, try and remember this! Good Luck!