There's so much mis-information out there on ich. Many people act as if ich is a virus like the common cold...that if your fish are healthy and eating they won't "contract" the "disease".
Ich is not a disease. It is a living parasitic organism that does not magically appear and make fish sick. It is brought in on infected fish, or on live rock, corals or sand that is hastily introduced. As Cediss and myself have said, this is more than plausible. It's science, but many argue otherwise by saying just to feed your fish more and keep them happy. Even if your fish don't show signs, ich will be in your system to infect all newly stressed introductions of fish and create a subsequent outbreak. People, it's not magic.
I had a bustling reef of beautiful fish over a year ago. I bought my ORA Hawkins Blue Echinata from a LFS and introduced it to my system without a dip or quarantine. I QT all my fish for ich prior to DT introduction. Within days my prized Achilles Tang came down with ich and deteriorated fast. I lost hundreds of dollars in fish. It was a low point for me in the hobby. After going back to the LFS a few weeks later I noticed that one of the three coral display tanks had a sick fish in it with ich. The owner of the store apparently believes that putting a sick fish in reef clean water miraculously cures them. Many have died in that tank from ich per employees' confessions to me when I spoke of my losses. I bought my Hawkins from one of the plumbed in tanks to this system. It was my only addition in over a year. After extensive research I learned that ich definitively can come in as tomites in the larval stage from another tank or the wild, only to wreak havoc on our livestock. Just because your fish don't show symptoms does not mean they beat it. They are simply not showing symptoms. We as hobbyists create these theories to keep us from doing the necessary dirty work of quarantining all new arrivals.
If there were any merit to not properly quarantining "ALL" new arrivals, then public aquariums would never waste the resources in quarantine and medication expenses, yet they do it as protocol, not on a case by case basis. I've been behind the scenes at 2 public aquariums and it's admirable and enlightening to see the lengths they go to ensure fewer losses. In fact, I feel that we as hobbyists should be allowed to periodically take a tour behind the scenes to see the operation at work. It's remarkable what makes something on that scale tick.
My best advice is to quarantine everything that is introduced into your system, and avoid buying coral from hobbyists or online retailers with fish in their systems if you aren't going to dip and quarantine.
