What is the difference between Ph and KH if PH measure Alkalinity?

[rhite]

The reason I ask is that I added a CO2 system to my tank to help new plants. In the instructions it told me to test the KH regularly. If PH measures alkalinity isn't that the same as KH?

 

[jcardona1]

Even though some say ph is a measure of the acidity or alkalinity of the water, it's not the same as your KH. The ph scale goes from acid to alkaline, hence the term alkalinity. KH is a measure of your buffering capacity, or carbonate hardness. Very different from ph.

 

[rhite]

Thank you! I love the help I get here. I am trying new things with various tanks to try and eventually set up 300g the way I want it. I am finding it is much less expensive to test on smaller tanks before killing everything or creating catastrophic results in one large one. I am my own, and my fish's, worst enemy at times. LOL. Thanks again!