Originally Posted by tobes3
I thought the goal with quarantine was to keep stressed fish away from other fish because they are more susceptible to diseases, won't putting 2 fish in contradict that? And why 3 weeks?
The primary goal with a quarantine is to allow a 3 week observation period, so that any parasites which are present on the fish have the opportunity to grow large enough to be seen with the naked eye. Anything less than 3 weeks and you are taking a risk that there are parasites present which have not exposed themselves for you to see.
I also agree that isolating a stressed fish from the display is important to allow the fish time to settle into captive life. This means learning the feeding schedule and foods provided, and being allowed a quite area away from the established pecking order of a display. I have never had issues adding 2 fish to a Q tank at the same time, probably because both fish are in a new environment. A pecking order does not come into play.
I would quarantine even the first fish. Why? Lets say you add the fish to the display, only to later see that this fish has ich. Ich can take a couple of weeks to be visible, so this is very possible, and occurs on a frequent basis in this hobby. So, you have now introduced ich into your display. Research is inconclusive on how long it takes to be "ich-free", but most of the recent reports suggest than an aquarium needs to show no signs of ich for 90 days if you want to be 100% certain the parasites will not reinfect the fish. 90 days. Plus, you have to decide how to treat a fish for ich in an aquarium with live rock and inverts. So, by placing a fish into quarantine for 3 weeks, you are elminating a lot of potential hassle.
One thing we have not discussed is a UV STerilizer. This is an optional piece of equipment that probably only 10-20% of us use. I am, however, an extremely big believer in a UV. The UV kills most disease causing pathogens, helping to prevent the spread of disease from one fish to another. I run a UV on my display tanks, including reef. I am such a believer that I would not run a marine system without one. I also spot treat my quarantine for a few days following the removal of livestock. You can buy a UV online for about $100, including bulb.