...Question now:
Should I take him out and QT Just him and monitor the others Or,
Should I leave him in there and hope it gets better Or
Should I take all the fish out and QT them. (Not a good option because I don't know if I can get them all out)
This is not an easy question to answer.
Certain tangs are, and always will be, highly susceptible to marine ich. The hippo is one of the most susceptible. What system he is in, what his diet is, and who his tank mates are all matter in terms of susceptibility.
In short, Ich has made it in to your display system.
It might have been there before you added the hippo, or the hippo might have carried it with him through treatment that wasn't completely effective. You don't have to see it for it to be there.
A similar situation happened to me with a PBT that I took through 8 weeks of hyposalinity. The minute I started raising the salinity, the ich returned. Thankfully, I caught it before I would have added him to the display (with hypo, you really have to go right to the edge for it to be completely effective).
What did you use for treatment and for how long? Was he in your display tank before you moved him to the hospital tank? What other fish are in there with him?
From what I recall, there are over a dozen different strains of ich that can be present in a marine aquarium. The good news is that each one that is eliminated from your system is one less to be worried about.
Back to your question, if you take him out of the display tank and treat him, he will be exposed to Ich the minute he returns to your display tank. He may or may not be healthier and better able to fight it off. If there is a drop in tank parameters, he may or may not suffer an outbreak again.
The only way to be truly sure that you eradicate ich is to remove all fish, treat them effectively for ich, and then return them to the display tank after it has sat fallow (without fish) for 8 or so weeks.
This is one of the great decisions that we all have faced at one time. There are many marketed products for supposedly treating ich, but many suspect these products simply make money off of the the hobbyist's desire for a quick and easy fix to a serious and difficult problem, akin to miracle weight loss pills, etc., that champion no need for that annoying dieting and exercise.
I certainly would not bother with raising the temperature. Tangs require heavily oxygenated water, and my experience is that they actually show an improvement in health with increased dissolved oxygen (raising the temperature lowers the oxygen content of the water).
As for garlic, it is an inexpensive try. I personally have never found it effective and I do not believe it works. UV can help a little, but a system would be quickly overcome in an outbreak. None of the other commercial products are completely effective.
Matt
