Alkalinity/Calcium imbalance

DiverDavid · Jul 31, 2018

So around 2 months or so back I was running about 8dkh and CA was around 410 ppm. So I increased my CA dosing. I am using the old BRS 2 part. Well I didn't test for about a month and a half and wound up with a 4.6 dkh and CA above 500 ppm. I am trying to slowly increase dkh but am thinking I also need to bring the CA down to do so. BTW my corals have been growing great even with the unbalance I just want to get it corrected. I want to make sure I am following the correct procedure and not going to get everything out of whack.

Thanks!

Crabs McJones · Jul 31, 2018

Let the calcium come down on its own, so only dose your alk solution to get your dkh back up to where you want it, and let calcium fall naturally until it's also at the level you want

DiverDavid · Jul 31, 2018

I have cut back on the CA dosing, don't really want it to drop too fast. I am assuming that is what you are saying?

HairyGary · Jul 31, 2018

DiverDavid said:
I have cut back on the CA dosing, don't really want it to drop too fast. I am assuming that is what you are saying?

Calcium drops very slowly so you should be fine for a couple days without dosing to get to the level you want.

DiverDavid · Jul 31, 2018

Correct me if I am wrong, the CA and Alk are inter-related, so if the CA is high like in my case and ALK is low bringing the CA level down should also bring the Alk up. Also I am wondering if I need to bump my Alk dosing up. I'm starting to confuse myself here...

NS Mike D · Jul 31, 2018

I believe mg has a lot to do with the balance of Alk and CA. If you have sufficient mg, then you should be able to raise alk to be in balance with CA.

My alk drops faster than CA for some reason. Mg is good. I haven't had an issue with CA levels when slowly raising alk. I should start testing alk more frequently to avoid the drops

Randy Holmes-Farley · Jul 31, 2018

It definitely won't drop too fast and 500 ppm is a fine level anyway.
There's no reason to try to bring down the calcium. It is not stopping you from boosting alk.

Nonchemists way overblow the effect of calcium on alk due to precipitation. The literature is full on nonsense in this regard. Misleading analogies like marbles in a bowl, for example.

The difference between calcium at 500 ppm and calcium at 425 ppm, in terms of calcium carbonate precipitation, is roughly the same as a pH rise of 0.07 pH units, which no one worries about. Maybe if they knew, they would worry and come up with new analogies. lol

Randy Holmes-Farley · Jul 31, 2018

NS Mike D said:
My alk drops faster than CA for some reason.

It always does, when calcium carbonate is formed. That is because there is a huge reservoir of calcium in seawater and not much alk. So when they drop proportionally (= 2.8 dKH (1 meq/L) for each 18-20 ppm calcium), the percentage drop is much larger for alk than calcium).