Dosing Phosphate raises Alkalinity?

speedinc

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hi reefers,

I dose Seachem Flourish Phosphorus to raise and maintain my PO4 level at 0.03ppm (measured using Hanna Phosphorus test kit). I figured out the daily PO4 consumption rate of my tank is 0.02ppm per day.

I have a GHL KHD and it performs 2 tests twice a day. I've seen my KH creep up from 7.9dKH to 8.5dKH over the course of 3 days though I have not increased my KH dosing. Sometimes it'll stay flat over 1-2 days and it will go up again.

So the question is does dosing phosphate actually increases KH? I read somewhere in the forum here commented by Randy that dosing Potassium Nitrate does raise KH. So i was wondering if this holds true for dosing Phosphate too.

Note: The ingredients of Seachem Flourish Phosphorus is derived from

amounts per 1g: derived from Potassium Phosphate
Available Phosphate (P2O5)0.3%
Soluble Potash (K2O)0.2%
 
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Randy Holmes-Farley

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Welcome to Reef2Reef!

That dosing wasn't the direct cause (assuming seachem does not include unmentioned alk supplements in it).

With phosphate, what you dose determines whether it causes a drop, a rise, or no change to alkalinity. Seachem doesn't provide the info to know. Dosing PO4--- (such as trisodium phosphate) boosts alkalinity a tiny bit. Dosing H2PO4- (such as NaH2PO4) lowers alk a tiny bit. Other formulations in between fall on a continuum from a depletion to a boost.

In all cases, the effect is much smaller than nitrate dosing because so little is dosed.

Adding 0.05 ppm phosphate with Na3PO4 will only boost alk by 0.0005 meq/L, or 0.00125 dKH.
 

Rob.bucek

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Welcome to Reef2Reef!

That dosing wasn't the direct cause (assuming seachem does not include unmentioned alk supplements in it).

With phosphate, what you dose determines whether it causes a drop, a rise, or no change to alkalinity. Seachem doesn't provide the info to know. Dosing PO4--- (such as trisodium phosphate) boosts alkalinity a tiny bit. Dosing H2PO4- (such as NaH2PO4) lowers alk a tiny bit. Other formulations in between fall on a continuum from a depletion to a boost.

In all cases, the effect is much smaller than nitrate dosing because so little is dosed.

Adding 0.05 ppm phosphate with Na3PO4 will only boost alk by 0.0005 meq/L, or 0.00125 dKH.
this is great info... I started dosing NaNO3 (food grade) to raise my nitrates until I can get more fish in my tank as NO3 and PO4 have been unmeasurable. I found this to be far more efficient and cost effective than many of the magic potions i was using previously. To that effect, I'm finding the same thing with PO4 magic potions. Can't seem to raise my PO4 above .03 for more than a day or so. Is there a straight up compound like NaNO3 that you'd recommend I can add for PO4 to get my levels up?

TIA!
 

Randy Holmes-Farley

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this is great info... I started dosing NaNO3 (food grade) to raise my nitrates until I can get more fish in my tank as NO3 and PO4 have been unmeasurable. I found this to be far more efficient and cost effective than many of the magic potions i was using previously. To that effect, I'm finding the same thing with PO4 magic potions. Can't seem to raise my PO4 above .03 for more than a day or so. Is there a straight up compound like NaNO3 that you'd recommend I can add for PO4 to get my levels up?

TIA!

Food grade sodium phosphate (several types are available):


 
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