Combined Ammonium Chloride / Diammonium Phosphate Dosing Solution

Dennis Cartier

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I am trying to calculate how much ammonium chloride, diammonium phosphate and sodium carbonate is required to create 1L of solution that will add 0.1 ppm ammonium and 0.01 phosphate when 1 ml is dosed into 100G and not raise or lower alkalinity.

I think it is:

121.28 g ammonium chloride
120.06 g sodium carbonate
8.43 g diammonium phosphate

I am trying to achieve about a 10:1 N : P ratio. I am not sure how much nitrogen ammonium actually represents. Also, I did not add any sodium carbonate to offset the diammonum phosphate as I don't believe it will lower alkalinity, but will the phosphate in it actually raise alkalinity?
 
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Randy Holmes-Farley

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If you want to assess the effect on alkalinity, you will have to make some assumptions about what is happening to the dosed ammonium (does it become nitrate, get incorporated into tissues, or get denitrified to N2) but in any case, it depletes alk. The only question is how much.
 

Randy Holmes-Farley

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OK, so ammonia to tissue is alk neutral.

Ammonium to tissue depletes alk. 1 mole of alk per mole of N dosed and consumed.

121.28 g of ammonium chloride is 2.27 moles.

120.06 g sodium carbonate is 2.26 moles of alk, so those numbers are good and offset.

The ammonium in the phosphate is another (8.43/132) *2 = 0.13 moles of alk

You'd need 6.9 g more Na2CO3 to offset that.

The phosphate itself is more complicated and depends on pH, but is reasonably close to net neutral for the form you used.
 
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Dennis Cartier

Dennis Cartier

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Randy, if I see an increase in alkalinity while dosing an ammonium chloride solution that has alkalinity balanced 100% for tissue/growth, can I assume that some of the ammonium is getting used in a way that does not require the offsetting alkalinity, and the increase in alkalinity is the result?

The reason I ask is that I recently observed an unexpected increase in alkalinity with my Alkatronic. The increase started 1 day after I had doubled my ammonium dose, from 0.36 ppm/day to 0.72 ppm/day. After observing the trend for 3 days, I assumed that growth was slowing, so I cut the ammonium dose to 0.54 ppm/day.

Upon closer inspection, I found a setting on a pump that had stopped dosing a nightly supplement, Dr. Tim's Coral Colors Recipe, along with Strontium and ESV Essential Elements (Fe/Mn/Zn). At the time I attributed the slowing growth to the interruption in dosing some days before, but upon reflection, I am wondering if it might have been an indication of dosing too much ammonium solution than could be incorporated into daily tissue growth.

Since cutting the ammonium dose back, and resuming the daily dosing of the bacteria and supplements, the increase in alkalinity has ceased and the daily consumption appears to be increasing over what it was originally, which I attribute to faster growth.
 

Randy Holmes-Farley

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I’m not sure exactly what it would mean if the dosing solution is adding alk and ammonia is not accumulating. I’ll ponder on that.
 
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Dennis Cartier

Dennis Cartier

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It looks like I will be dumping my remaining Ammonium Chloride/Sodium Carbonate solution and mixing up a new batch to include P.

I noticed that my growth had slowed and my corals were darkening, not browned out, but well on the way. I also noticed my daily pH was not going as high and my Alkatronic graphs were showing slowing alk consumption. I decided to test my nitrate, which I don't do as often as I should. It has been stuck at 0.2 ppm on Salifert and 0.0 on Hanna HR forever. Also the reason I have been dosing ammonium daily.

The Salifert test came back at 10.0+ ppm! So I ran a test using the Hanna, 10.0 ppm. This was the first time my Hanna registered anything but 0.0.

On a hunch I tested my phosphate. I had not tested it in about a week and it was 0.06 ppm the last time I checked. It came back at 6 ppb (0.018 ppm). Yeesh, no wonder my corals are browning out and the nitrate is climbing. My LPS are looking super happy, smiling from polyp to polyp, SPS, not so much.

I have disabled the daily ammonium dose for now and will be hand dosing Flourish Phosphate to bring the nitrate down and the phosphate up. There is always something ....
 
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Dennis Cartier

Dennis Cartier

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I have mixed up a new batch with the following parameters:

114.30 g ammonium chloride
120.06 g sodium carbonate
8.43 g diammonium phosphate

This should be closer to the 10:1 ration N : P that I am looking for, and accounts for the ammonium in the diammonium phosphate, and the offsetting carbonate required.

Once I swap this version in, I should only need to watch phosphate and the nitrate should settle into a complementary range. So instead of increasing the daily dose until I see detectable nitrate, how the old solution should have performed, increasing the daily dose to keep the phosphate within desired range should provide enough N to cover the daily P consumption. If my 10 :1 ratio proves to be a reasonable ratio that is.

I chose the 10:1 ratio based on Hans-Werner's suggestion of it here:


Note to (future) self: Drain the settled calcium phosphate from the bottom of the solution before attaching it to the dosing head. The precipitate WILL clog the 0.8 mm dosing tube.
 
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Randy Holmes-Farley

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Once I swap this version in, I should only need to watch phosphate and the nitrate should settle into a complementary range. So instead of increasing the daily dose until I see detectable nitrate, how the old solution should have performed, increasing the daily dose to keep the phosphate within desired range should provide enough N to cover the daily P consumption. If my 10 :1 ratio proves to be a reasonable ratio that is.

It will be interesting to see what the ratio is. Hardly anyone has such info that I have seen.
 

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