Very Low to Nill dKH - The Planted Tank Forum
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post #1 of 3 (permalink) Old 01-30-2019, 02:58 AM Thread Starter
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Hello. Finally got my tank up and running, it’s been about 3 months now. 47G acrylic with 1” of Onyx Sand under 1” of Flourite Black Sand. Multiple pieces of Seiryu and Ohko Stone. A good size hunk of Mopani driftwood and a piece of regular driftwood. Running a Marineland Emperor 400 HOB with sponge pre-filter, bio-balls and sponge in compartments. A Fluval 206 canister with Sponge pre-filter and ChemiPure Green. Injecting CO2 via a Sera CO2 reactor. Using a Current USA Satellite Plus Pro for lighting. I have an auto doser adding a general fertilizer (Easy Green), an Iron Fertilizer (Easy Iron) and a Carbon Fertilizer (Easy Carbon).
I have multiple different plants including dwarf baby tears. All plants are doing wonderful. My CO2 drop checker is a consistent lime green. All my livestock appear happy and healthy.
My issue KH has vanished. Last measurement (about 6 days ago) I had a dGH - 7
dKH - 4
(Now, I should say that I have been injecting CO2 these last 7 days and I’m sure that’s what’s probably causing this...but I’m not THAT sure)
So today I checked my parameters and my dGH went up to 9
dKH dropped to about 1 or less.
Onyx sand says it’s supposed to support proper KH levels...but I’m guessing that must just be sales pitch.
Anyway, Ammonia & Nitrite are zero... Nitrate is negligible. pH is running about 6.5.
Why has my KH vanished? Is it the CO2?
I use RO water that I remineralize with KHCO3, CASO4 & MGSO4. I set the values of that water @ 8 dGH and 4 dKH.
Am I freaking out over nothing?
I get that everything is doing well, so why mess with it...but it bugs the snot out of me that the KH is so low.
Any suggestions? Maybe a little crushed coral in my HOB?
Any advice would be appreciated
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post #2 of 3 (permalink) Old 02-01-2019, 06:52 AM
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I'm not sure why KH is dropping as Onyx sand has extra KH and black sand is inert. Also, those stones are known to increase KH as well. The wood will release tannins which can reduce KH, so if there are a ton of tannins, that could explain it.

Really, KH is not important. It doesn't take much to maintain pH (like less than 1 dKH). The only real issue with low KH is if you use a pH meter or keep livestock that really need high pH (like sulawesi shrimp or something).
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post #3 of 3 (permalink) Old 02-03-2019, 09:02 PM Thread Starter
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I spoke to a LFS and was advised to reduce my CO2. They said that’s what’s eating my KH. I’ve lowered it and have been watching for the last couple days. pH has been pretty stable and after slowly raising the KH it seems to be holding. So hopefully that’s what it was
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