If you use RO or distilled water you NEED CalMag Plus

[Revanche21]

If it is not RO/distilled. Then you need an EC/PPM meter. Besides PH your EC/PPM are most important. You might be good to go. My bro has well water under 100ppm's. Works good with hard water nutes.

Depending on the filter and the source of water, will answer your question.

Remember if it has chlorine in it it has one function. To kill organic matter.

It is a pain sometimes getting water but well worth it in the long run of getting over the big hurdles of hydro. RO units can be gotten cheap.

When you know you started with nothing to screw you up then it is alot easier to fix problems.

Once I got my meters and water straight problems went away.

I didn't use a PPM meter in my grow o_o