Read your art.'s/ 2 ques. on pH adjmts

[RJPII]

Hi Randy - Can you please help me understand something better?(sorry for the lengthy thread to start) I have just read two of your recent and very helpful articles (What your grandmother never told you and Low PH problems) and have also refreshed an older article(resolutions to the various Ca/Alk. scenarios). I still have two questions that I wanted to ask before I study them further.

Before I ask, after two years of learning, I seem to have gotten myself into a puzzle. For most of this time, my pH has usually ran 8.35 - 8.45, being measured by a meter. About a month ago, it dropped to 7.85-8.05. I strongly suspect excess CO2 and am going to be checking this and still have work to do for the long run fix of supplying better Oxygen. In the meantime, my calcium has been plummeted to a consistent 200-250ppm.:confused:, while my Alk. has been 2.00 to 2.9. Prior to a month ago, when I previously dosed with Bionic my pH would often go above 8.45, so I started leaning heavy on CaCl (Turbo C.)

My questions:
1. I read in your art. ('what your grndmther')that Calc. Hydrox. can combine with Co2 to actually reduce pH. Does this mean dosing limewater would not be effective in supressing high Co2 in select curcumstances? if so, which? I may have missed the full point on this one.
2. At that point in time when my pH started to drop, I had an event where many of my elect. appliances seized up within a couple days. (two powerheads, my skimmer pump and my SCWD wavemaker) Do you think this was a sudden build of calc. carbonate? I did notice more crusty white build up and a rough sandy buildup on the exterior of the pumps. Do you think this was related? I have since tried to balance it more w. limewater dosing and Bionic, but the Ca. is still VERY short at 200ppm this morning. My system has approx. 120 g and yesterday I increased to dosing Bionic to 96 ml/48 ml (CA/ALK) and two tbls of Turbo Calc.

Thank you in adv.
Bob

[Randy Holmes-Farley]

Does this mean dosing limewater would not be effective in supressing high Co2 in select curcumstances?

No, it is always among the most effective ways of raising pH. It does combine with CO2. That is how it reduces excess CO2 in the water and thereby raises pH. :)

Do you think this was a sudden build of calc. carbonate?

Could have been, but low pH usually results in lower deposition, not more.

You'll need a lot of calcium chloride to raise the calcium level. I don't know how it could have gotten that low without a lot of alkalinity only additions. Precipitation cannot lower calcium that much without added alkalinity.

[RJPII]

On my first ques. - OK - Limewater generally raises pH. (glad to hear this....I must have got confused on that one!)

On the carbonate precip. issue, I don't believe I did any kind of large scale Alk. buffer dosing. Keep in mind that my pH was actually on the high side when my calcium started to drop (and when I think some kind of event jammed my pumps)

I was thinking that perhaps the Ionic balance was thrown off when I went away from Bionic and Kalk and dosed heavier with the Turbo Calcium.

ALSO, I noticed that my magnesium has dipped to 1150 again. I had a low level like this around that event. Perhaps this played more a part in this. I thought I had corrected it, but must have errored in my testing (Salifert). I will work to correct this to start and will check my pH monitor calibration once again as well. (I learned the Borax method from this forum as well)

Thanks

[Randy Holmes-Farley]

I was thinking that perhaps the Ionic balance was thrown off when I went away from Bionic and Kalk and dosed heavier with the Turbo Calcium.

I can't think of any way that calcium can decline except by adding a lot of alkalinity. To remove 200 ppm of calcium would require the removal of 10 meq/L (28 dKH) of alkalinity, which is far more than is typically present.

That said, the way to fix it is to add more calcium chloride. This calculator and article will help:


http://home.comcast.net/~jdieck1/chem_calc3.html

Solving Calcium and Alkalinity Problems
http://www.advancedaquarist.com/issues/nov2002/chem.htm

I'd boost the magnesium up. Low magnesium can increase the likelihood of calcium carbonate precipitation, but again, the alkalinity is necessary for that process.