Mysterious Red Spots on Surfaces in Aquarium

I have something gowing in my 20-gal. freshwater aquarium. It is some kind of red stuff that builds up in spots on the glass and other surfaces. If you would like to see a piture of it I posted a photo on alt.binaries.aquaria in a message titled "Red Spots on Surfaces," dated 10/15/2004, 10:23 AM. The photo shows it on a decorative rock. After I changed the water and cleaned everything by rubbing with salt, it appeared to be cleared up, but it soon came back. It started as just one or a few small spots, but the spots grew and multiplied. I am tempted to throw away the whole setup and start over, but I would first like to know what this stuff is and whether there is any way to get rid of it permanently.

Rick E. suggested asking about it here. He said there is a lot of expertise here, and you guys could likely help.

Any ideas?

Thanks,

Hal