Normal KH drop?
I started up a new 110 gallon aquarium with a 40 gallon sump two days ago. It was moderately to heavily planted. The KH has dropped 4 degrees, and I am wondering if this seems normal.
Here are some specifics:
My tap water is from a well, and about 6-7 KH, 7-8 GH depending on the day.
The current KH reading is 3, using two different tests. (Hagen, Red Sea)
Substrate is a bottom layer of 50/50 Flourite and Terralit, Top layer a mixture of Flourite Dark and Estes Bits o' Walnut gravel. (All of these substrates are inert as far as I know, I know substrates like Amazonia soften water though)
There are 3 larger pieces of malaysian driftwood in the tank. My suspician is these are the main culprits.
pH currently is reading 6.6, and CO2 has been injected to maintain ~25-30ppm.
A half dose of Flourish, and all 3 NPK Flourish products was added on the first day.
Does this large a drop in KH in 3 days seem normal? I don't mind 3 KH, but am trying to get a handle on what is happening in the tank. Will it continue to drift down? Will the driftwood (or whatever) eventually lose some of it's acidity and stop buffering it down? Any other thoughts?