I agree with George, but sometimes the solution is to keep the fish in a tank large enough to house them, and transfer the other critters to a smaller, more manageable tank for the duration

Good luck with whatever you do :smile:

So then what would you recommend. I would rather stay away from copper and keep the stress to a minimum for the fish

Who are you responding to ?

All. I still have the 175g that I could bring online and do hypo in instead that way there would be no rock or sand to deal with but I can't dose copper in that tank as I plan to sell it soon. What method would be the best to treat them. I also have an empty 80g that I could use but again no copper allowed.

I'm in the 'no copper' group, so I vote for the Hypo routine
I'll stress again ... 1.008 worked for me. 1.009 can border on the limits of resistance, so do as you will

Whether you remove your fish, or remove your inverts corals and LR is up to you

Whatever makes your life easier and makes the most sense

I know you're looking for an answer, but you have to make up your own mind

Put all your fish in one tank, and the rest in another :razz:

Every time I have used hypo, I was 100 % successful. I did have some live rock, and the bristle worms died, but that's all I noticed. I didn't have much for pods in my QT. With all the water changes to get the salinity down, and a mature canister filter, I didn't have any water quality issues.

Of course this was in 30g QT, so can't say what will happen in a large DT full of live rock.

As has been already stated here, and I will say it again very emphatically, be sure to get it down to 1.008 or 9. Use a calibrated refractometer. And keep it there for at least 6 weeks.

If you do this, please let us know how it works. I have never heard of anyone going hypo with a large DT.

If you have a spare 175 lying around, I'd drain the DT to get the fish out. I've drained my 180 a couple times now and it's not a big deal if you have something to hold the water for 20 minutes. Siphon out with a 2" dia. hose, pick out fish, pump water back into tank. House them in a temp smaller tank where you can manage treatment better.

Is there any preferred method of treating

I would recommend the hypo as well
you will have some die-off of the worms and such..but the bacteria should be fine as it can adjust to hypo conditions
I personally would take the corals and inverts out with a 1/3 of your life rock
drain half your tank and fill it up with fresh water
sounds scary..but I have done it numerous times
you can than adjust your salinty the next day to bring it down to the .009
(probably about a 1/3 of your tank to be emptied and filled again with fresh water)
leave it like that for 6 weeks just to be safe
and slowly raise your salt over a 3 day period.
I have done it numerous times without problem
I wouldn't recommend copper for ich
if you notice the fish still have ich after a week..then copper is required because you would have one of the rare strain of hypo-resistant ich

if you treat your fish without LR in whatever style you try, you will have to be doing substantial and frequent waterchanges which would be probably problematic for such a long period of time.

A list of methods to treat/QT for marine ich based on order of my preference:
1. Tank transfer
2. Copper
3. Hypo
4. Chloroquine Phosphate
and yes, I tried them all. :)
There are pros and cons for each method. Make sure you read them all (not only this site but some other sites as well) before you pick one. Above all, understand the life cycle of marine ich is very important regardless which method you pick.
Good luck.