The water I am putting in has a TDS around 4. So the only thing I can think of is the slime that is in the tub. I will try to cover it and see if that helps.
I was putting ro/di water in a large 100 gallon rubbermaid tub with a heater and a small pump to use for topoff and water changes. When I checked the TDS it was around 20. I noticed when I drained the tub it had algae growing on the sides which is what probably raised the TDS. Any suggestions...