New GFO reactor is reducing phosphates and large increase of calcium

[Jstn]

I have previously run the BRS reactor with GFO for the past 2 years, my PO4 numbers have been struggling to drop below 0.15-0.2 ppm, despite changing the media once a week. With the reactor off my return pump I could only get 10 GPH (neptune flow meter) and it would channel the media. So I moved up to a Avast spyglass which fluidizes the media (now HC GFO) much better and I can control the flow upto ~150 gph without issue.

Now for the interesting part, over the last week of setting up this reactor my Calcium has risen from 450 to 630 via trident, and it increases daily. For the last week I haven't dosed calcium and even turned off my AWC. My salt mix, Tropic marine pro, is currently 440 via Red sea test and not know to be a high calcium salt.

I think this is attributed to the improved PO4 removal that is liberating Calcium from calcium phosphate precipitate in the tank from previous ineffective removal from previous method. And since its in equilibrium with free PO4 and Ca, this would explain the rise.

I am looking to verify if this logic makes sense and when should I worry about calcium levels, at this rate they are rising ~20 ppm every 12 hrs, I started AWC back again since replacing water with lower calcium NSW should work in my favor. Any other ideas to help lower or at least stabilize the calcium levels?

 

[Randy Holmes-Farley]

I suspect something else is happening. I do not think GFO cannot cause calcium to rise that much. I don’t believe that calcium phosphate dissolution can explain a rise of that magnitude.

I’d focus on verifying the measurement before focusing on lowering calcium. A rise in its own is not happening. Something is adding it if it really is rising.

 

[dwest]

Could GFO be decreasing alkalinity, thereby reducing the usage of calcium?

 

[Jstn]

I suspect something else is happening. I do not think GFO cannot cause calcium to rise that much. I don’t believe that calcium phosphate dissolution can explain a rise of that magnitude.

I’d focus on verifying the measurement before focusing on lowering calcium. A rise in its own is not happening. Something is adding it if it really is rising.

I agree with you randy that this increase would be hard to explain by Ca3PO4 dissolution, I did verify with Red Sea kit and salifert (600 and 620 iirc) I have not dosed in a week and yet my tank is super happy.

To verify it is the gfo I have decreased the flow to ~50 GPH, if the Ca levels off it could test my hypothesis

Could GFO be decreasing alkalinity, thereby reducing the usage of calcium?

generally I was 80ml a day of 1.0 M Na2CO3 and 80ml day of 1.0 M CaCl2, the alk consumption has risen to 85 mL/day. My mag is dropping 10 or so points per day (with in the test margin of error) and is around 1350.

 

[Randy Holmes-Farley]

Could GFO be decreasing alkalinity, thereby reducing the usage of calcium?

GFO can accelerate the precipitation of calcium carbonate which shows up as some increased demand for both.

thousands of people use GFO and do not see big increases in calcium. That, and the lack of a mechanism for it to happen, is why I suggest looking for other explanations.

 

[Jstn]

GFO can accelerate the precipitation of calcium carbonate which shows up as some increased demand for both.

thousands of people use GFO and do not see big increases in calcium. That, and the lack of a mechanism for it to happen, is why I suggest looking for other explanations.

I agree with you and why I am questioning my own ideas. The only difference in my case would would be the drastic increase of flow to the reactor and due to my high po4 locked in the system from poor reactor performance and elevated po4 “bound in the rock”. Mind you I have had issues w cyano and PO4 for over a year.

I am continuing to explore other plausible reasons. I was hoping it was a test kit error which explains 99% of erratic parameters.

I will report back in a few days if I can chase
It down. Thanks for the help!

 

[Randy Holmes-Farley]

Another way to think of the hypothesis relating to calcium phosphate dissolving is that for calcium to rise 50 ppm by dissolution, the GFO would have had to bind more than 50 ppm of phosphate. That would take a huge amount of GFO, even assuming it could happen.

 

[gmichaela]

What was the outcome of your calcium issue? I have exactly the same issue and I have ruled out all of the obvious reasons for a calcium spike from 440 to 615 except for possibly the GFO or dry rock creating this issue.

 

[Mkeller088]

I have more verification of this exact issue. I also have a trident. I have been maintaining calcium at 440 for months. Alk at 9.5, and Mag at 1350. All good. No GFO, and phosphate at 0.07. Nitrate runs high at 60.
I added BRS HC GFO (2cups) in a bag today. My Calcium jumped to 519 in a few hours. Alk had little movement, 9.32. Magnesium dropped to 1320.
The GFO did this without question. I don’t know why, but there is no doubt the exact timing of adding GFO and seeing this is not a coincidence.

 

[Mkeller088]

I think (dangerous) that GFO reacts with trident reagent, or actually does spike calcium. It’s late, I’ll re test tomorrow and post.

 

[Mkeller088]

Just re tested 9.2, 438, and 1350. Everything‘s back to normal. Really strange.
I know calcium didn’t make that kind of swing. I can only suggest the test is skewed by the GFO for at least the first few hours.

 

[Randy Holmes-Farley]

FWIW, I do no see how GFO would cause incorrect calcium readings. I think it is most likely coincidence unless a lot of powder GFO wasn't rinsed out and clouded the water.

 

[Mkeller088]

The issue never came back. I agree that the rinsing was not done real thoroughly.