what days??and what PPM is fine????

whats different of the EC and PPM?

Ppm is an expression of ec, just in different numbers. Here's a chart.

The reason there are a couple different numbers is because some ppm meters are calibrated to different equations of Ec.

A .7 conversion ppm meter when measuring 1ec of nutrients solution would display 700ppm while a .5 conversation meter measuring a nutrient solution of 1ec would display 500

700/7= 1
500/5=1

Same ec, different numbers, different ppm meter calibration.

Sorry, that's not right. Just took a dab. Anyways, it's:

700ppm/700 (7 conversion) =1ec
500ppm/500 (5 conversion) =1ec

770ppm/700=1.1ec
550ppm/500=1.1ec

And so on.