# Flourite Black Sand dumping GH and KH



## jonny_ftm (12 Feb 2010)

Hi,

Facing difficulties to lower my GH and KH in my RCS 45L, I made this test:

I filled half of a drink glass with Seachem Flourite Black Sand. Added RO water (KH 0.6) to fill the glass and stir it. After 3 weeks, I tested:
*KH 5.4
GH 8*
 
Just shocked. Is this how my tank would go if I didn't make weekly 50% WC? Seachem insist that their substrate is inert. I had really big doubts seeing how much calcium carbonate it holds, but trusted them.

I'm very angry as I really targetted a lower KH than my actual 2.4. Also, I hate those swings of making 50% WC with a KH of 0.6 and it always ends in 2.2. I'm not sure my RCS appreciate this, especially the babies.

So, despite its success, I would never recommend it again


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## a1Matt (12 Feb 2010)

If you did not do any water changes (I am not advocating this, just describing what would happen) and did not add anything to raise the GH and KH they will slowly drop as the plants use up magnesium + calcium (for GH) and carbonates (KH).

I'd be inclined to just do WC as usual and let it slowly reach an equilibrium with the water introduced by the WC.
If the livestock looked shocked by the change then fill up slowly.


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## jonny_ftm (12 Feb 2010)

I don't think KH and GH will drop even without WC. The soil looks really saturated and leaking tons of Ca and CO3, maybe Mg. In few days, GH and KH raise in my tank. Probably it is the equilibrium between water, soil and plants uptake in my case.

I just can't explain why Seachem claims their soil is inert or no significant change on KH and GH when a simple test shows the opposite: it is a calcareous soil


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## Themuleous (13 Feb 2010)

Does being inert cover it 'leaking' things?  Inert means it wont react, which I guess taken to the letter its not, its just releasing stuff into the water?

Just a thought.

Sam


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## jonny_ftm (13 Feb 2010)

No

Seachem insists it won't affect KH or GH quiet at all.

I'm discussing it now on APC in seachem sponsor subforum. They think I have a bad bag, not sure really since no one before tried what I did.
I'll let you know how the discussion goes about it on Seachem but they're showing a good support


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## Themuleous (14 Feb 2010)

Fair enough, just a thought 

Sam


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