I am going to try to be helpful here and not get on a soap box! This comes from spending literally hundreds of hours dealing with a velvet outbreak 3 years ago, and the long road back. And lots of reading on Humblefish and R2R.
You should assume that any fish you receive, from any source, is carrying parasites that will wipe out your tank. There is simply no way to know otherwise. Unless you, personally, eyeball it in QT daily for the required period of your QT protocol, you just cannot know. And the heartache from a velvet or brook wipeout can drive you from the hobby. (Hence, the healthy resale market for tank systems). It is just not worth it. I promise you. Go to Humblefish or R2R, and find a QT process that works for you. Mine involves therapeutic copper for the entire prescribed period, prazi, and an introductory parasite dip. And observation. Have not had a single speck of anything on my fish since I did that. But you need to read up to find the protocol that works best for you.
QT is not as easy as popping a fish in your display. I understand that. But I promise you, it is worth the time and costs almost nothing. Yes, you have the space. Don't kid yourself. If you've got a reef tank with reactors and lights and skimmer and sump and R/O station (which you do, right?) then you have room and money for a simple QT setup. Do note that it needs to be a moderate distance from your display to avoid aerosol cross-contamination. I treat it as part of the rehoming process. Make it fun. Spend special time with your new critter. Make sure you watch ammonia and oxygen levels, so QT only 1-2 fish at a time in lots of water. Yes, you will lose some fish in QT . But those fish almost certainly were not going to make it in the DT either, and possibly take everyone else with them.
Keeping healthy fish is SOOOOOOOOOOO easy. It is the corals that are hard, LOL. Seriously, I have not bought a fish in more than a year. I have no room, and my display tank is 200 gallons. That is your goal: to be out of the fish buying trade because they never die. Pro: my fish are indestructible. Con: I have no reason to go look at fish at LFS any more.
Nothing goes in my DT unless I am 100% sure that it is free from parasites. No public aquarium manager would ever just plop a fish in the display tank. Their mortgages depend on it. Protect your display tank fish like your mortgage depends on it. Like you would lose your job if there were an outbreak. It is so worth the time and effort.
in your tank on arrival. Nothing really is as effective as a QT set up on premises.
