I think the Naso, being a wild caught specimen, was freaked out being in a small space (small to him at least). That combined with the stress of being caught, hitting the LFS
, and then to you, was enough to lower his immune system to let ich get a foothold. Also, many LFS
's keep the salinity of their water at .017 or so, which will keep parasites from taking over. That's fine and dandy, until you get them home and introduce them to your water...
I think moving the hippo from the 75 to this QT was enough to stress him out too. I would have waited and watched to see if anyone else got a bad case of it before I moved them. My hippo had a couple spots on him when I introduced him, but they went away and haven't been seen since. This has always been the case for my additions except for one fish- an Achilles tang.
I figure that the environment of least stress is the one that looks most like their natural habitat.
A naso is probably one of the last tangs I would consider for a 75. I would stick to the round bodied tangs for now, like scopus, yellow, purple, or one that stays somewhat small like a kole.
I know my methods aren't the popular way, but I've had good luck thus far.
That skimmer is way underpowered also. I'm sure you know that, but just in case..