Question about PH/KH and CO2

Lampshade · #1 01-14-2012, 10:27 PM

I noticed a couple of my fish this morning gasping for air. I immediately pointed powerheads at the surface and ran some tests while I got a water change ready. When I ran the tests in the beginning I showed a KH of 16dkh. This seemed VERY high seeing how my calcium was normal at 420ppm. My KH/Calcium have always been pretty balanced, and I run a calcium reactor and dose kalk, so they stay fairly balanced.

Anyways, I started to wonder about possibly a bad test, so i re-did the test. MY KH was back at 9-10dkh, right where i like it. This seems better, but it's such a simple test I don't think i could possibly screw up counting drops from one bottle. I also noticed EVERYTHING in my tank doing much much better, coral polyps where back out, fish where no longer stressed and gasping. So I assume I had very low oxygen in my tank.

I"m thinking that my very high CO2 levels would give me a false high KH level? My PH went up about 0.2 during this from 7.9 to 8.1 over an hour.

I know with planted tanks there's a close relationship with KH/CO2 and PH. I was wondering someone knows if the same goes for salt water?

gregzz4 · #2 01-14-2012, 11:31 PM

CO2 affects pH for sure, but it has no relationship with KH. If someone can show otherwise, I'd like to have a read.

Lampshade · #3 01-14-2012, 11:37 PM

Here's a site about planted tanks. http://www.thekrib.com/Plants/CO2/kh-ph-co2-chart.html Found it interesting, but not sure if the same would apply to saltwater since the alkalinity is much different because of our water having so many other substances.

gregzz4 · #4 01-14-2012, 11:46 PM

I ran planted on all 3 of my FW tanks before deciding to make the change-over this last fall. I never found anything or any reading that showed a relationship between CO2 and KH.
KH affects pH for a short while after a dose, and CO2 affects pH, but that's all I can tell ya, besides the fact that I've never seen anything on pH swings changing KH.
Hopefully others will either back me up or show some info to dispute my learnings.
Sorry I can't help ya with the KH discrepancy.