The good news:
Following the excellent instructions posted on the list
last week by George Janini, and also by reaching into
the tank by hand with a soapy rag and scrubbing, I have
cleaned out the green slime and black crud that coated
the water tank in my recently purchased '87 Westfalia.
Even the hoses look a lot better - not 100%, but hopefully
good enough not to poisen us.

The bad news:
Now my water level sensor doesn't work.  It used to.
Now it always reads "full".  I suspect I damaged the float
rod somehow - it took a fair amount of wiggling to get it
out of the tank.  I suppose it's also possible I somehow
electrically damaged the monitor panel itself, although that
seems less likely.

The symptoms:
  - Water level always reads "full".
  - Battery level indicator works fine (I think).
  - "Fridge pilot on" light lights when fridge pilot is on.
  - "Fridge pilot on" light also lights whenever the pump
    is running.  Odd.  I don't know if it did this before or
    not.  Does anyone know if this is just a Westfalia
    idiosyncrasy, or something unique to mine (and
    thus probably indicating a problem in the panel).
  - I thought the "fridge pilot on" light also used to light
    when the fridge was running on 12V (with the engine
    running).  Perhaps I imagined it.  In any case, it doesn't
    now.  Does anyone else's do that?
  - My manual says that turning off the panel switch should
    also disable the pump.  Mine doesn't, and never has.  I
    assumed it was an error in the manual, but ?
  - Wire connectors look OK at the tank end.  (No obvious
    shorts or breaks, at least.)

Any thoughts or suggestions?  Anyone know a source for
a replacement sensor rod or monitor panel?

Thanks.