m0useanswered grow question 2 years ago First figure out what it stops read out at. Mine is 2000ppm, or 4ec.
Then like other said, give just water.
If you use a flushing agent, it will bind to the molecules and make them unavailable to the plant but will see them react to a TDS pen as its testing how conductive the solution is, not really measuring the parts per million. Can use the flush water in a veg garden if you have it. just dilute it down and spread it aorund, something might as well get use out of it.
Good Luck!