pH and Calcium Precipitation

[Dono]

Hi All!

As I’ve posted in previous threads, I’ve had some low pH issues in a relatively new tank. Severely low pH originally caused by a stupid mistake of dry ice storage in the house but ongoing CO2 issues with a tightly sealed condo and poor air exchange.

My problem now is heavy calcium precipitate while tuning my 2-part. My alk is generally in the mid 8s to low 9s, calcium is actually a bit on the high side (440-460), and pH is fluctuating from 8.05-7.7 generally (this is with a CO2 scrubber and new media every 2-3 days ... short term solution).

My question is what’s he relationship between my low pH and precipitation? I’ve had alk/calc levels around here before with no similar reactions. I read through some of Randy’s articles and might just need a bit more of an ELI5 breakdown.

Thanks,

Ed

 

[chipmunkofdoom2]

I believe low pH would have a tendency to prevent precipitation, not cause it. The drop on the calcium graph before the 18th was likely testing error. There would have been a huge drop in alkalinity at the same time if there was a precipitation event.

What is your magnesium level?

 

[Dono]

Mg was 1375 last I checked but I’ve only texted once this month since it typically doesn’t drop rapidly in my experience. Do you think the mg could be low causing a lack of a buffer for ca/alk and making precipitation easier?

 

[chipmunkofdoom2]

Mg was 1375 last I checked but I’ve only texted once this month since it typically doesn’t drop rapidly in my experience. Do you think the mg could be low causing a lack of a buffer for ca/alk and making precipitation easier?

No, not at 1,375 ppm.

What's the concern? You mention there's precipitation, but calcium and alkalinity aren't trending in such a way that would suggest precipitation events?

 

[Dono]

That’s what’s confused me. I can visually see precipitation on my heaters and pumps and wasn’t sure if there’s a relationship between low pH and increased precipitation.

I haven’t ruled out bacterial blooms but there are no other signs that it would be bacterial.

Ita a real head scratcher

 

[Randy Holmes-Farley Verified Community Expert]

Precipitation on heaters and pumps is normal because heat decreases the solubility of calcium carbonate.

Lower pH reduces the chance, as does lower alk and calcium. pH is a huge driver. A drop of 0.3 pH units is equivalent to dropping either the alk or calcium by half.