Mixed Dosing Mixup?.. P and Kalk

BeejReef · Oct 7, 2019

So, a quick question.

I dose P to my tank. I've had to. Without the dose it drops to 0 and my nitrate will quickly climb. I use a fuge as my primary nutrient export. Typical levels are N 18-22, P .08-.14, Alk 9dkh, Calcium 430, Mag 1380

In the past, I've been able to regulate nitrate by adjusting my fuge photoperiod and adjusting the P dose up if it was getting exhausted.

The past few months, I've been mixing my trisodium phosphate in with my saturated kalk reservoir. I dose this with a single head doser.
My nitrate numbers now seem less responsive to increasing phosphate levels.

Is the trisodium phosphate somehow bonding to my limewater and becoming less available to my macro-algae fuge, or am I just reaching the limits of my fuge's capability?

ty

Iván Olalla · Oct 7, 2019

Yup, kalk somehow precipitates phosphate bonding to it, tried the same you did with my doser and no levels increased, so i put my potassium nitrate and phosphate additions in my ATO with calculated evap/contribution and worked like a charm

BeejReef · Oct 8, 2019

Iván Olalla said:
Yup, kalk somehow precipitates phosphate bonding to it, tried the same you did with my doser and no levels increased, so i put my potassium nitrate and phosphate additions in my ATO with calculated evap/contribution and worked like a charm

I had a feeling. Just watched a MACNA video at BRS Channel and the presenting chemist was talking about phosphate bonding with calcium (I think, not great memory) and it got me thinking. I'm still able to see phosphate in my testing, it just seems like it's not as available to my macro algae.

Iván Olalla · Oct 8, 2019

BeejReef said:
I had a feeling. Just watched a MACNA video at BRS Channel and the presenting chemist was talking about phosphate bonding with calcium (I think, not great memory) and it got me thinking. I'm still able to see phosphate in my testing, it just seems like it's not as available to my macro algae.

Do you test for other elements like potassium and iron? Macros consume more of this than corals. A few years ago my scrubber was growing algae, but it turned out with a yelleow tint, not the forest green i was used to, also sps were kind of finicky at the time, after some tests i added some iron and everything went back to normal

BeejReef · Oct 8, 2019

Iván Olalla said:
Do you test for other elements like potassium and iron? Macros consume more of this than corals. A few years ago my scrubber was growing algae, but it turned out with a yelleow tint, not the forest green i was used to, also sps were kind of finicky at the time, after some tests i added some iron and everything went back to normal

Thanks for the tip. Actually, I do. I just got back an ICP. Thanks to some rusty hinges, I have PLENTY of iron.. lol. Potassium was in the green. I think I was a touch low on molybdenum.