Diagnosis Please

[RWCrouch]

150 gal FOWLR. Water parameters all normal though nitrates are high (recently, last Sunday through Tuesday, had a dino bloom and did lights out except for 2 one hour sessions per day for 2/1/2 days to feed the fish). Dino is gone, tank is frankly beautiful, did water changes and nitrates are back down to about 20 ppm, they were higher from the dino kill-off I expect. Emperor foxface has a single raised round white spot that appeared overnight. Larger than what I am accustomed to for ich (about 3-4mm) and its midbody. All fish are otherwise healthy and active. Gills clear and healthy, no flashing, etc.

I did add one new fish recently, but it was divers den from liveaquaria which are frankly more quarantined than anything I am equipped to do here myself. I have seen ich before and this just doesn't look or "feel" like ich. Possible small injury? Some other type of parasite? Photo attached, though not the best of pictures. Will try for a better one if it helps. Ideas?

Also, quarantning this fish probably not an option. He is about 6 1/2 inches and my hospital tank is only 20 gals. Then there is the whole problem of trying to catch a fish in a 150 g tank with 200 pounds of rock in it. Will be more inclined to treat the whole tank if it comes to that.

 

[nonstopfish]

I would just observe for a few days and see what happens. Hard to tell from the pic, but I definitely agree it is too large to be ich. There is really no such thing as "more quarantined", lol, it was either quarantined and treated or it wasn't. At Diver's Den the fish aren't treated unless they absolutely need to be, so any fish that comes in from them can/will have parasites, etc. Does it look like it is attached to the fish or something pushing up thru the skin?

 

[RWCrouch]

pushing up from underneath; he is losing a scale from there now . . .

PS -Divers Den does treat prophylactically according to their site