Gravel Fungus! Please Advise!

[TireTrack86]

There is a white fungus in my tank that grows rediculously fast. Hours. I noticed this on my platys the day before yesterday, and since then it appears to have gotten worse on them, and killed my guppies and swordtails. I have what were labeled as rose barbs at the lfs and they seem to be immune so far. The black tetras that I thought would also be fine are coming down with it. I find that even more strange since I thought they were the source, since they've been nipping the fins of my other fish. -planned on exchanging them today-
Here is more information that could help solve the problem, and does anyone know what I can do? Thanks!

I bought a -presumably- used fish tank from my lfs that contained some used gravel. Apparently there were turtles in it as the gravel contains the cuticle portion of the plates on the turtles' shells.

 

[Lotus]

It sounds like a fast-moving bacterial infection. You should be able to get some antibacterial medications from your local fish store (LFS) to treat the tank with. They generally have descriptions/pictures of the various diseases to help you match the symptoms to the medication.

Make sure you do water changes after the medication course is finished. Remove any dead fish as soon as possible.

 

[TireTrack86]

Thanks very much. I'm taking what's left of my fish to the lfs until I get the situation resolved.