I just moved into a house a month ago with a well with very hard water. The toilet tanks had a slimy black build up on the inside. I cleaned it when I moved in and even with regular use, the build up is there again.

At first I thought this was a effect of the hard water, but it looks more like bacterial growth. Yuck.

The water has been smelling pretty badly of sulfur in general, even with a Provector (sp) sulfur treatment system (uses air to turn sulfur to solids, then filters the solids out). I had the system fully evaluated and cleaned out, filters replaced, etc. three weeks ago.

I put a cup of chlorine tablets down the well yesterday, in an attempt to get at the root of the problem.

My question: is the build-up in the toilet tank likely a matter of bacterial growth in the well, from neglect of "shocking" the well?

Is there any additional step I should take in the tank to prevent build up?

The toilet tanks had a slimy black build up on the inside. I cleaned it when I moved in How did you clean it?
Did you remove all the water and scrub it down with full strength bleach? Let me know, Tom

I removed 95% of the water and scrubbed the sides and parts with a stiff bristle brush. Used toilet bowl cleaner. Someone had told me I would ruin the gaskets if I used bleach in there.