Originally Posted by Tom Barr

One, the GH is basically 2 plant nutrients, Ca and Mg.
KH is not.

KH, or alkalinity determines pH. We artificially lower pH with CO2 gas, tannins etc, so pH in and of it's self is not critical, nor the real player here.

KH is.

This can and does influence uptake of various nutrients, some plant's enzymes are optimized at lower pH's(think KH though!!).

It's not just CO2 uptake that will help these plants, you have to make sure it's the KH.

Most plants are fine at high KH's, their enzymes are okay with the higher alk levels transporting nutrients in/out etc.

All plants are fine at low KH's on the other hand.
Thus in aquatic systems, KH, rather than pH is the real player in uptake preferences.

Note: traces in general are more available at lower KH's, while macro nutrients are more available at moderate to hard water(KH here, not GH)

GH is what folks remove when they soft their water with salt, the KH is very high, but very low GH.

Regards,
Tom Barr



Regards,
Tom Barr