"Nemo" wrote in message ...
What water chemistry parameters would you ideally want in a planted tank?
pH, kH and gH?

My kH is very low, about 3 dKh causing pH swings. I want to minimise raising
the pH. What is the minimum kH needed to maintain a reasonably stable pH?

Thanks

The issue is not so much an ideal pH, it's more an issue of the proper
CO2 level.
See pH/KH/CO2 chart/table= www.sfbaaps.com

KH is fine 2-3 degree range.
If your pH is moving, it's moving for a reason, CO2.
The plants remove it, the pH goes up. At night, the CO2 from the air
slowly re enters the water and equilibrates the pH back down.
GH/KH are good in the 3 and up range. I am unaware of any upper limits
as few folks have KH's above 20 or GH's above 25 and I've kept plants
just fine in that water, so it's unlikley you'll encounter water
harder than that.

If you do not add enough CO2, the plants will sometimes, depending on
the species, go after the KH for the carbon, all algae can do this as
well.
If you only have say 1 degree of KH, if the CO2 is too low etc, then
you can use up all the KH.
Doing routine regular water changes prevents this depeletion along
with having enough KH in case this happens.
Also adding enough CO2 will also prevent this.

Do you have a non CO2 plant tank?

If you use CO2:, GH/KH 3 degrees or higher.
pH= depends on the KH when adding CO2. See table, the two are
related, not independent measurements when trying to provide good
conditions for plants to grow.

It's all about CO2, that is what plants prefer(pH/KH combo).
GH= just enough Ca++/Mg++ which are nutrients so the plant does not
run out.

Regards,
Tom Barr