I find that by and large most people who have problems with quarantine are simply doing it wrong.
That said, there is no cookie cutter one size fits all method that works for all species. Proper qtine is a science all to itself.
I used to be a professional aquarist. The very idea of NOT quarantining is unthinkable to me. I've seen the end results of such failure too many times.
So, to answer the question, yes, quarantine is essential. You might be able to get by with a big UV unit and an oxydator, and running some ozone in your skimmer, but those won't solve ALL of the potential problems.
When it rains on the reef, big puddles of fresh water float around the place. You can spot them easily, because fish flock to them to give themselves freshwater baths.
Yep. Those of you who think that freshwater dips are terrible should know that the fish like to use them in nature.
I mention this because the freshwater dip should be the first thing you do, even before you put the fish into the quarantine tank.
A little container will do, but make sure the water temperature is in the 70's and that it's been well aerated. You'll want a pH in the mid to high 7's.
Put the fish in for as long as you see it isn't in distress. This can be a surprisingly long time, but about 8 minutes is about the maximum limit.
Then put the fish into your quarantine tank.
THEN wait about an hour, and look on the bottom of the freshwater container. What you will find will forever convince you of the usefulness of the freshwater dip. Each one of those dead parasites represents hundreds to thousands of parasites that won't be born in your tank.
Next, let your fish have a couple of days to settle in before treatment.
Look for signs of bacterial and fungal infection.
Copper causes infection to flare up like crazy. Thanks to the freshwater dip, you have the luxury of not having to worry about parasites so much for awhile, so you can begin treatment for worms and infections first.
You don't have to use copper for most of the ickies. There are other options available that are gentler but still effective. Garlic and Herbtana work wonders.
You'll still need to use copper for a few parasites which are too tough for anything less, but one thing at a time. You don't want your fish to be swimming in a toxic soup from using too many meds at once.
During quarantine, you should give more freshwater dips every two days, or even daily if you can.
In fact, you can rid a fish of ick completely using nothing but a series of dips if you want to get crazy, moving the fish to a new tank after each dip. Eventually all of the parasites will drop off with no chance to be replaced.
That's a lot more work than most people will want to do, though. I did it regularly, but my facility was set up for that.
Oh, it should go without mentioning, but it takes at least 24 days to get rid of the ick/velvet parasites. I know that a lot of products on the market promise a cure in three days or not much longer, but this is a lie.
What I'm getting at is that if you want to kill the parasites, you have to understand them. When they're embedded in flesh and covered in slime, you can't kill them. They're only vulnerable during certain times in their lives, and with a 23 day lifespan, you should be able to catch them when they're exposed at some point in 24 days.
Most of you guys should already know that, of course, but there's always someone who doesn't.
Ick on the body is relatively harmless. It's the ick on the gills that kill the fish. Freshwater dips are for killing the parasites in the gills. The ones on the body are not going to be affected much. This is why you dip repeatedly; the idea is to keep the gills clean.
Oh, another thing- those who think a fish is fine because they don't see any spots would do well to bear in mind that they can't see the gills. This is how "healthy" fish in the store suddenly "get" sick when you take them home. SO many illnesses aren't readily visible, so just assume that the fish are sick, because they almost certainly are sick.
