Having most trouble QTing wrasse

[Deinonych]

if heat/O2 is the main factor, shouldn't both fish show symptoms of labored breathing?

I seem to always lose 1 out of the pair... sometimes male, sometimes female..

better results when QTing individual wrasse.

1 thing for sure is I'll never save salt money again.. will fill the 20 gallon full from now on.

If the problem only occurs with pairs, I think you have your answer.

The one time I tried to QT two wrasses at a time (two male Paracheilinus of different species), one mysteriously died all of a sudden. I think one them (a P. cyaneus which I still have) bullied the other so much it died. Wrasse social hierarchy is based on dominance and submission, so that's probably what's going on with yours. Best to stick to single specimens at a time IMO.

 

[MellowReefer]

I don't think it's a problem using only 10 gallons of water as long as you don't overfeed. I recently put 3 male wrasses through TTM using 10 gal tanks and I only filled up to 7 gallons most times. The first day I fed light (but 3 x per day), 2nd day a little heavier, 3rd day before transfer fed heavily. By the third day it was a little cloudy. I added a little amguard on days 2 and 3. I used frozen hikari mysis that was rinsed in rodi so it was very clean and only fed other messier foods on day 3 right before transfer.