I do roughly 6 weeks QT sometimes a bit longer. Basically the sooner they get in the DT the better. Water quality is better.
I do 40 days hyposalinity and it has worked flawlessly for me. I've never had a parasite in the DT. I also dose Prazi now although I've never seen flukes or had an issue. Can't hurt to add another layer of preventative medicine.
The biggest killer in QT is water quality in my experience. This is because most quarantine tanks have a very weak biologocal filter. There's usually no (or not much LR) to provide denitrifaction so nitrates get super high, ammonia can spike, algae blooms etc. I have some LR in mine plus I have a few sponges in there that act the same way as LR but it will never be as good as a well setup display (wih fuge/denitrator/DSB/zillion pounds of LR). Therefore uneaten food and fish poo needs to be manually removed as often as possible. I try and clean twice a week which involves removing everything, scrubbing it down, scraping tank and doing a 50% water change. And then every day I'll siphon bad stuff out.
A few weeks ago I didn't siphon and after one week without a water change the bird wrasse had popeye. It eats a lot and so does the larger Emp so I'm generally feeding heavier than normal anyway so there's lots of excess food and fish crap that if it isn't removed, rots and fouls up the tank.
Fish that survive my QT are hard as nails and disease/parasite free. I only ever lost one fish due to disease in the DT and that was the adult Emperor last year that died of a swim bladder infection (probably due to water quality issues as I didn't change water for 3 months but even then, who knows). I've lost loads of fish in QT, I don't deny that. But it's better than feeling helpless as a parasite devours your precious tank. My success rate would be a lot better if I was more attentive to QT husbandary but who likes to spend 2 hours scrubbing tank, powerheads and rocks? Certainly not me, but it really has to be done. This year I have had a renewed energy for the tank so I'm riding that wave to get loads of new livestock in - hopefully without too many losses. As long as I get my Emp pair, pair of Regals, harem of Grammas and a clown tang everything else is a bonus. Failed on the regals and grammas in the past so I really want to get it done. After that I'll be focused on pairing smaller fish like a pair of Sixline Wrasses, Orchid Dottyback pair, Longnose Hawk pair. I love to see paired fish interact.
So lots of good stuff ahead. This hobby is awesome.
