While I'm new here, I can only tell you what works for me so far, which doesn't mean it can't change. This is my first time with SW as well, so after some reading, I decided to buy the biggest tank I could find. I ended up with 125 gallon tank, bought some nice live rock teaming with life and purple, toss some corals in there a couple of weeks later and fish by the 3rd week.
I decided to buy a QT after the tang got ich. But by the time the QT was established it was a bit too late for that tang.
That tang was with a couple of clown fish in the QT under the copper treatment and I can say all three got quite tense in the QT. After the tang died, I waited a day or so and observed the clown were still stressed, not to mention the ammonia levels were always high, with required almost daily massive water changes. I had to pull the 2 clowns out of the QT and put them back in the main tank. One clown survived the move and one died shortly. He has gasping for air even before the move.
While the fish were in the QT, I set up a UV sterilizer in the main tank, running at a very low flow rate to take care of the ich. After placing the fish back in the main tank, I added a second, much more powerful UV sterilizer as well to the main tank.
I'm running my QT empty for now and monitoring it's levels, and so far the ammonia is under control and NO2 & NO3 are getting lower but not quite there yet. So I've decided any new fish will go in the QT once it's ready, which I'll also add a small UV sterilizer to it that will run only when there is fish in it. Everything for now is in the main tank including some new hardy fish I've added that didn't go through quarantine. I am depending on the UV for now.
In conclusion, I would say if you have any fish in the main tank, transferring them to QT could stress them out even more so. All new purchases are recommended to go through QT for a week or 2 depending on their behavior. I would add a UV light at least in the QT. Like I said, I'm new to this and what I did, may not be the best recommendation. But I've found these fish can stress out very easily and need to feel secure in a comfortable environment with no disruption. If adding a UV light is what it takes at the cost of beneficial bacteria, then so be it.
The LFS in my town all run UV lights on/off for 2 week periods. That's my intention at this point.
Sorry for the long post. Hope my mistakes would benefit you.
cheers
Wael
