GFO calcium carbonate precipitation

[Randrew215]

Over the past month, I've had to increase my 2-part and have been dosing 460 cc of Ca++ and Alk for the past two weeks. The increase has been due to falling parameters, though since my dosing regimen has been this high, I've been stable at about 420-450 for Ca and 9.0 dKh for Alk. What I have noticed in this time is increased growth from my corals but also a precipitate that has formed of my heater as well as in my GFO and GAC chambers. When I cleaned them last week with a vinegar bath, the bubbling that ensued confirmed to me that it was CaCo3 (versus perhaps a bacterial bloom for carbon dosing). Already, I can see that the precipitate has reformed and my efflux from the reactors has diminished. There are several threads on reefcentral with this exact same issue with productive feedback from Randy Holmes-Farley and TMZ, but I didn't see anything that followed a corrective course with resolution. I've halved my two part dosing and will report parameters and presence or precipitate until I get things balanced out. I should also mention that I don't dose anything else for Ca/Alk and that I dose into the last chamber of my sump, with the reactors in the chamber before.

On a separate note, I found out on Friday that my girlfriend and I both matched into residencies in Buffalo and will be here for the next four years (and beyond)! Good for my tank, good for my life.

 

[tmz]

I'd make sure the magnesium is a bit on the high side ,ie around 1400 plus.
It can slow abiotic precipitation of calcium carbonate. I'd also consider changing the dosing site and pace for the alkainity dose ,so it can mix well with the aquarium water before hitting the gfo ,heaters or pumps. Cutting back on the dose a bit seems prudent too.

 

[Gary Majchrzak]

x2

x2

running Ca on the high side (450+ppm) can cause problematic precip

400ppm seems to be a good target for me

 

[MD Ocean Girl]

As a medical student myself, I want to give both your girlfriend and you a HUGE congratulations on matching in Buffalo!!!! :celeb1::thumbsup::dance:

 

[TomBONAIRE]

Congratulations on your matches. Specialties???

 

[Randrew215]

As a medical student myself, I want to give both your girlfriend and you a HUGE congratulations on matching in Buffalo!!!! :celeb1::thumbsup::dance:

Thank you!! I don't know what year you are but fourth year was described to me as the 'most expensive vacation you'll ever take,' and I have to say it is actually pretty awesome. If you come out this way on the interview trail or just in your travels, let me know!

Congratulations on your matches. Specialties???

Thanks! I'll be in emergency medicine and my girlfriend will by neurology

 

[Randrew215]

So, I reduced Ca and Alk dosing to 250 cc/day on the 17th. On the 18th levels tested at ca: 430, Alk: 7.7. Did a 20 gallon water change that evening and didn't measure again until today when Ca was 400 and Alk was 8.6. Also, on the 18th I cleaned out both reactors (GAC and GFO) which were almost completely clogged with calcium carbonate precipitate and vinegar soaked them. No signs yet of any newly forming precipitate and tank looks happy overall. I'll test tomorrow or the day after to see if things remain stable, but it definitely appears I was over-dosing.

 

[TomBONAIRE]

Great choices. Love the vacation line........

 

[Randrew215]

Update: From 3/17 to now I've maintained Ca and Alk dosing at 250 cc/day. Calcium has remained between 370 and 430, alkalinity between 7.7 and 8.6. I am no longer getting noticeable precipitation on my GFO or GAC.
But... when I was in NC for a week, I fielded calls from my girlfriend that one of my vortechs had stopped (vacation day 1), the skimmer pump failed (vacation day 3), and my return pump failed (vacation day 6). She was able to get the return running again and I had to wait until Saturday to look at the others. Everything was gunked up with calcium carbonate. I've vinegar soaked the powerheads, return pump, heater, reactor pump, and skimmer pump and everything is working great again. I definitely lost some coloration on my SPS while I was gone though, so we'll see how long it takes for those to turn around.
I guess what I've learned is that all of the heat-producing equipment is going to draw excess calcium and bicarb out of the water column and eventually cause equipment failure, which makes the balance between under-dosing and over-dosing slightly more complicated. I'm going to see if I can continue to lower my dosing volumes a bit more without a further drop in test values.

 

[tmz]

The heat reduces solubility . The water holds less calcium carbonate in solution at higher temps; so when saturation levels and pH are very high precipitation occurs in these areas first .
Magnesium can help discourage some of it and should be kept at at least 1300ppm ; I prefer 1450ppm or so. Magnesium will jump on some carbonate molecules instead of calcium. When it does the forming calcium carbonate crystal stops growing.;thus slowing precipitation an keeping more calcium and carbonate in solution. Not a ton of difference but enough in many cases to limit the type of precipitation you were getting.