Kalk Reactor & pH Swings

[Fish76]

I just started a Kalk reactor (stirrer type, Aqua Medic 1000) a couple days ago. I waited to get my calc/alk to where I wanted before bringing it online. Currently:

Alk 8.624dkH (Hannah)
Cal 443ppm (Hannah)
Mag 1155ppm (Salifert)
SG 35.1ppt (Apex)

My mag is a bit low and I'm waiting to get BRS mag solution delivered on Tues to target around 1250ppm. I started with a small mix bag from BRS and didn't realize it takes much more volume of mix to raise mag than it does for alk/calc.

I have my Apex setup so that if my pH is above 8.3 top-off comes from pure RO/DI reservoir. If the pH is below 8.3 top-off comes from the Kalk reactor. My top-off runs about every 2-3hrs and dumps about 1/4gal give or take each time. When top-off comes from the Kalk reactor, there's an increase of pH of about 0.1 each time (within 5min). My question is, is this too much of a drastic increase eacht time the Kalk reactor is used for top-off? Looking at my Apex logs, my top-off seems to alternate between the RO/DI and Kalk reactor throughout the day. With this setup, my pH hovers between 8.27-8.41 throughout the day/night and my Alk/Calc have been pretty consistent.

 

[Randy Holmes-Farley]

pH 8.3 sounds like an excessively low cut off. I'd personally set it above 8.5, if I were to use a cut off.

A 0.1 pH unit jump with each addition is not a concern, IMO.

 

[Fish76]

pH 8.3 sounds like an excessively low cut off. I'd personally set it above 8.5, if I were to use a cut off.

A 0.1 pH unit jump with each addition is not a concern, IMO.

Thanks Randy! The thinking behind setting the pH to run the Kalk at 8.3 was that if I did set it to 8.5 and say pH was 8.49 the Kalk reactor would still go on and potentially raise it to 8.6 or higher since I've seen an increase of 0.1 within 5min during a top-off cycle. You think it would still be safe to have it go on that close to the 8.5 limit? I was trying not to exceed 8.5 based on you parameter recommendations. So setting it at 8.3 the most it may go would be around 8.4.

 

[Randy Holmes-Farley]

Ah, I see. The response time is not fast enough to stop the 0.1 pH unit rise.

I'd probably still up it to 8.4. I ran my tank for years at pH 8.35 to 8.55 without any apparent problems. But if you get enough limewater to meet alk demand with the lower limit, that's certainly fine.

 

[Fish76]

I think what I'll do is keep my settings what they are and monitor alk/calc. If I find they are slipping, I'll raise the pH setting as you suggest to dos more kalk. My main concern was having spikes in pH in short bursts, happening throughout the day, but as you indicate shouldn't be a problem. Thanks again!