_MG_6892 by DancingWisp, on Flickr

So this is a Diamond tetra that I have had for about 4 weeks. He has a white compact yet fluffy growth/thing on his bottom jaw. It appeared yesterday and doesn't seem any different today. He is eating, and is active. He hides just a bit more than the other diamonds (total is 16).

Water parameters are:

amm<0.25 (for me this is 0 as I have a weird contaminant in my water supply that makes amm show positive)
temp 25.5

Stressors: We had moved 16 bloodfins over from QT to this tank on the weekend. I also added 8 glowlights (without putting them in QT first, yes I am a moron!).

Is this columnaris (there are no strings off of it) or a fungus? I am getting him in QT today and will treat with whatever is appropriate.

Also, how do I get one tetra out of a 77 gallon tank with 39 other little fish? I know it is kind of funny, but I want to help the guy out by isolating him and cannot do that if I can't get him out of the tank!

Thanks in advance...