'and a TDS of 110 is too high for a tank'
in a US metropolitan area us 300-400 ppm
. That reading does not mean the concentration is all nitrate/phosphate or silicates. Testing is the only way to determine that.
Although I don't, lots of people use tap water and have minimal if any algae issues. I venture a guess that some use RO
and still fight algae issues as well.
As I said, I would consider a TDS
of 110 a great number for municipal tap water, not knowing what the levels of nitrate/phosphates and silicates are