Quarantining fish if suspect tank already has ich
 

Realize you QT for more than just ich but something I been wondering (sort of brought forward here again). As it's almost accepted that our tanks have ich, though maybe not showing, is it worth the effort to set up a longterm QT for a new fish?

More for discussion as not planning any fish but my case, seen some spots last year on a tang and nothing since but I'll assume my tank has ich (as it's never been fish fallow). If I was to get a new fish, considering stress, a NH3 spike, etc, is 4 weeks in a QT really worth to risk?

Personally, I don't quarantine fish, nor would I ever. My existing fish are fat and healthy, and they can manage their own health. I expect the new addition of a Tang would result in some ich, but it's to be expected and my tank provides the right atmosphere to reduce stress (clean, lots of hiding spots, etc).
My last tang was a large RS Sailfin. He looked salted by the time I got him home. Fed garlic on nori, 30 hours later, no sign of ich. It's been a couple of months now, everyone is fine.

I recently added a Wrasse, no issues.

For me though, I'm full at 5 fish (although just one more Tang might be ok)...

I used to QT any fish that looked like they had any sort of disease, being that I have reef tank (a pain to try to catch a fish once in there) and my other fish like to bully the newcomer. As of late though I've been just adding my purchased fish into my display tank and if Ick appears I found No Sick Fish Ick medication has worked well for me.

This used to be my philosophy as well until a couple weeks ago. Having had trust in the quality of livestock from my usual retailer, I added a new fish straight to my reef after a moderate acclimation (~20-30 mins). The new addition has long since expired and 3 out of my 5 fish are critically ill with ich and velvet (one is already MIA).

IMO if a fish has already spent 3-4 weeks at the retailer and looks healthy then I think the risk of a system wide outbreak is much lower than with new arrivals. Of course you may be relying on the accuracy (or inaccuracy) of store staff info as to how long the specimen has been there.

As everyone knows, this hobby is not inexpensive and maintaining separate QT and hospital systems can be highly impractical. However, I think that every decision making process should include a 'general risk assessment' as well as asking the question 'to what degree am I willing to risk a major wipeout.' In my case, depending on the final outcome, I will be taking a serious look as to whether I will be continuing with this hobby. Caveat Emptor.

An excellent cautionary tale that should give pause to anyone. I agree that it comes largely down to a cost/benefit analysis. The vast majority of stuff you add to the tank won't cause any ill effects whatsoever. It's that one in a hundred that causes the trouble. I think of QT as insurance - you DON'T get insurance because of what will PROBABLY happen, you get insurance for what is UNLIKELY to happen. Whether it is worth the time and effort to buy the policy depends on the state/value of your tank and its inhabitants, the origin/type/state of the livestock you intend to add and your ability to establish a QT for the period of time required.

I'd QT it....it may have something other than ich

I quarantine for more reasons then to get rid of ick. I have a big tank with a couple of very active, aggressive fish and everything I get has travelled at least 6hrs in a bag (usually 24hrs). If I were to dump a fish directly into the display I'd probably never see it again.
My quarantine tank has subdued lighting and is in a room that only I go into. The fish has a chance to settle, check out his surroundings and to gain some much needed fighting weight before being tossed into the lions. I also get a chance to look at my purchase and ooh and ahh over it, it could still disappear in the display never to be seen again but at least I've had 6 weeks of quality time with it before it disappears :razz:

My achilles, the regal angel and the copperband all went through quarantine and I believe they are all the better for it

I put a tang in QT last weekend, showed signs of HLLE, so i said screw it and into the DT he went. I pulled him out 2 days later because he looked like he was rolling in the sand, covered in white spots. He will be in my QT for at least 6 weeks. If any of my other fish (2 clowns and a foxface) shows signs of ich in the time the tang is in QT, then i will pull them out and have a very expensive fish tank with no fish, and a bunch of crappy smaller tanks with one fish each!

I dont think a QT is too big of a deal, simple HOB filter and a heater and a small PH and bam there ya go. I was worried at first that my new fish would be stressed out more being in the QT, but he has been in for 4 days and he has settled in nicely.

Also, it is a royal PIA to pull a fish out of a tank with out traps or baited hooks! So from now nothing goes into my tank unless its 100%.