Normal KH drop? - The Planted Tank Forum
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post #1 of 3 (permalink) Old 10-25-2007, 06:33 PM Thread Starter
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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?
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post #2 of 3 (permalink) Old 10-25-2007, 08:12 PM
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Yes yes and yes,

Your KH decrease is common, nothing to be worried about. Your Driftwood probably has a lot to do with it. Its not just he driftwood though. Over time there are a lot of naturally occurring acids in a fish tank that will lower your buffering capacity. I am sure one of our scientists will show up to explain the organic processes that take place.

The good news is that IME it doesn't matter. My water out of the tap has 0 degrees KH and the PH in my tanks is in the low 6s without CO2, somewhere in the mid 5s with it. No body cares. I did more damage stressing my fish with PH swings trying to keep up the KH that finally I gave up and I realized it was all for nothing. Every bodies happy at a low PH. I just have to watch when I introduce new fish and acclimate them slowly. I do have to dose magnesium and calcium to prevent deficiencies, but those are GH, not KH. If you are worried throw a handful of crushed coral in your filter, that will help.

Don't mess with it is my advice.

The plural of anecdote is not data
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post #3 of 3 (permalink) Old 10-26-2007, 03:51 AM Thread Starter
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Ok, thanks for the reply. I actually prefer a softer water, so a lowering of the KH is fine with me. I just was startled by how quickly it dropped in a couple of days. I wasn't really expecting that.
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