In your alls opinion, if you have one fish which gets ich, should you pull them all out. See my problem is I have a lot of fish, and it would be immensely hard to get them all, what should I do?
Each situation is different. In theory yes, once it in your system every fish could get it. Most the time a healthy fish will get over it on it's own. In my case the stress of a new fish added to the problem.
What I would do is watch the fish to see it it get better. If it get worst or start to spend than pull him and any other with ick. That's what I did... in my case it just happen to spread to all the fish. I also had it where it will just pass with time.