I have drained my jacuuzi and found a dark film that is very difficult to remove.Any ideas how to remove it?

I was away from the jacuzzi for 3 weeks, and suspect that my friend had not been treating the water.


(It is normally treated with bromide tablets, muratic acid and Ph up and down chemicals, as well as having an ozone apparatus built into the system.)


Could this be the cause of this film build up?


The water is heated by a propane heater.|||Try using liquid diswashing cleanser. Soak it. It may be mold.