I checked on my tetras last night and I noticed that my smallest looked like he had a whitish clear patch over his back and part of his sides right behind the dorsal. Perfect timing because I'm leaving tomorrow morning on vacation and won't be back until sunday. Its kinda hard to tell if its bacterial or fungal, or maybe he just hurt himself on the lava rock. I'd really hate to medicate the whole tank, especially since I won't be there to make sure everything's going okay. The other inhabitants are pretty sensitive too...I've got 2 ottos, a sparkling gourami, and four more black neons. I'm cleaning the tank today, but do you think I should isolate him and treat him with fungus clear, or just leave him in the tank until I return? I don't think I've got an extra working heater.... I'll be back later with more details, the computer's about to kick me off.

I take it the neons are new to the tank? How long have you had them and have they been quarantined?
Neons are susceptible to a lot of diseases and the most prolific is Neon tetra disease. Does the fish look washed out at all? I would also consider saddleback columnaris and false NTD. I would seperate it asap.

Eek, I'll separate and medicate him tonight. I'll keep him in my parents bathroon while I'm gone since that is the warmest spot in the house. The newest fish has been in there since summer, and the affected black neon looks and acts fine otherwise.

Ah didnt realise it was a black neon. Well i doubt neon tetra disease though it can be seen in other fish. I would treat for columnaris just now and see if it spreads. Keep the tank as cool as you can without the neon getting too upset and treat with bacterial meds.

The white patch is gone and healed, and he looks great! Do you think it's okay to add him back to his tank with his buddies?