Dosing phosphate - NaH2PO4 or HNa2O4P?

[Wilz]

Greetings!

I have just started dosing phosphate using Seachem Flourish Phosphorus, but I figured that I should follow Randy's suggestion and make my own stock solution.

Can you please take a look at the following and advice on whether I should get Mono Sodium Phosphate Anhydrous or Sodium Phosphate Dibasic?

APC Pure

APC Pure is a leading chemical and reagent manufacturer

apcpure.com

Sodium Phosphate Dibasic | Chemicals | APC Pure

APC Pure supplies Sodium Phosphate Dibasic ACS Reagent in all pack sizes for all applications

apcpure.com

Many thanks!

Cheers, Wilson

 

[Randy Holmes-Farley Verified Community Expert]

All three forms of sodium phosphate (Na3PO4, Na2HPO4 and NaH2PO4) are fine if adequately pure. Both of what you list are adequately pure.

The only differences are very minor adjustments to alkalinity. Na3PO4 will very slightly raise it. Na2HPO4 is about neutral, and NaH2PO4 will very slightly lower it. None of the effects are big enough to worry much about since doses are small.

 

[Wilz]

Many thanks Randy!

Do they have roughly the same amount of phosphate? Just trying to figure out a suitable concentration for a stock solution. I have a Red Sea Reefer 350 so approx. 300 L of water.

If I want to have a stock solution that I can add say 5 ml to raise phosphate by 0.01 mg/L. How many mg should I dissolve in 1 L of RO/DI water?

 

[Randy Holmes-Farley Verified Community Expert]

Many thanks Randy!

Do they have roughly the same amount of phosphate? Just trying to figure out a suitable concentration for a stock solution. I have a Red Sea Reefer 350 so approx. 300 L of water.

If I want to have a stock solution that I can add say 5 ml to raise phosphate by 0.01 mg/L. How many mg should I dissolve in 1 L of RO/DI water?

The differences are much smaller than unknowns such as how much will bind to rock and sand, but the NaH2PO4 has slightly more than NaHPO4 which has slightly more than Na3PO4.

 

[Randy Holmes-Farley Verified Community Expert]

You can use this calculator for dosing and solutions, and use the entry for potassium phosphate. Then just use slightly less (77% of the recommended amount).

James' Planted Tank - Dosing Calculator

 

[Wilz]

Thanks Randy. Using Jame’s dosing calculator for potassium phosphate, I figured that if I make a solution using 1g of mono sodium phosphate in 500 ml of RODI water, and at 77% of the potassium concentration, a 5 ml dose gives about 0.015 mg/L phosphate in my tank.

 

[neiltus]

following so I don't ask the exact same thing in 3 weeks.

 

[Reefs anonymous]

You can use this calculator for dosing and solutions, and use the entry for potassium phosphate. Then just use slightly less (77% of the recommended amount).

James' Planted Tank - Dosing Calculator

not to hijack the thread, but I have a question for randy. I got trisodium phosphate and am trying to use this calculator. I’m mixing 1/2 teaspoon to 3 oz ro water. Based on this calculator, if I add 1 drop if this solution to 50 gallons of water, the phosphate should increase by 0.01 ppm, correct? I currently added like 100 drops and I still have zero phosphate. I’m using salifert test kit that’s expires in 2021. I’m confused. What am I doing wrong?

 

[Randy Holmes-Farley Verified Community Expert]

not to hijack the thread, but I have a question for randy. I got trisodium phosphate and am trying to use this calculator. I’m mixing 1/2 teaspoon to 3 oz ro water. Based on this calculator, if I add 1 drop if this solution to 50 gallons of water, the phosphate should increase by 0.01 ppm, correct? I currently added like 100 drops and I still have zero phosphate. I’m using salifert test kit that’s expires in 2021. I’m confused. What am I doing wrong?

If you mean you add it to a reef tank, it is likely binding to the rock and sand. That is normal and expected, and make it take a while until you see left over phosphate.

 

[Kevind0905]

Hi Randy. Looking for a product I can use to dose phosphate and found this on Amazon. Just wanted to see if it was Reef safe. Thanks.

Disodium Phosphate [Na2HPO4] 98+% Food Grade Powder 4 Oz in a Bottle USA

 

[Randy Holmes-Farley Verified Community Expert]

That looks like a good choice.

 

[Reefs anonymous]

If you mean you add it to a reef tank, it is likely binding to the rock and sand. That is normal and expected, and make it take a while until you see left over phosphate.

Thanks randy, I finally got a phosphate reading after 200+ drops over a few days. I guess I just monitor it’s from here and add as necessary. I’m also dosing nitrates you about 5-10 times phosphate, which I’m measuring something about 0.03ppm. My nitrates are just about 2ppm.

 

[Kevind0905]

Hi Randy. Looking for a product I can use to dose phosphate and found this on Amazon. Just wanted to see if it was Reef safe. Thanks.

That looks like a good choice.

Thank you!

 

[Randy Holmes-Farley Verified Community Expert]

Hi Randy. Looking for a product I can use to dose phosphate and found this on Amazon. Just wanted to see if it was Reef safe. Thanks.

Thank you!

You're welcome.

Happy Reefing.

 

[Randy Holmes-Farley Verified Community Expert]

Thanks randy, I finally got a phosphate reading after 200+ drops over a few days. I guess I just monitor it’s from here and add as necessary. I’m also dosing nitrates you about 5-10 times phosphate, which I’m measuring something about 0.03ppm. My nitrates are just about 2ppm.

IMO, 2-10 ppm nitrate is a good level for any aquarium.

 

[NDIrish]

All three forms of sodium phosphate (Na3PO4, Na2HPO4 and NaH2PO4) are fine if adequately pure. Both of what you list are adequately pure.

The only differences are very minor adjustments to alkalinity. Na3PO4 will very slightly raise it. Na2HPO4 is about neutral, and NaH2PO4 will very slightly lower it. None of the effects are big enough to worry much about since doses are small.

Do you dose for phosphate, if so what do you use for dosing phosphate?

 

[NDIrish]

Randy, Found this. Would it be good to use?

• 

Roll over image to zoom in


Disodium Phosphate Food Grade Minimum 99% Purity! 1 Pound
by JJ Chemicals
5.0 out of 5 stars 2 ratings

Price:

$12.50 & FREE Shipping

• Also available in HDPE bottles for sturdier packaging.
• Anticoagulant
• Anti caking additive

Specifications for this item

 

[Randy Holmes-Farley Verified Community Expert]

Do you dose for phosphate, if so what do you use for dosing phosphate?

I never needed to dose phosphate to maintain appropriate levels. I think any food grade sodium or potassium phosphate is fine.

 

[Marc K]

I have chased up a source for sodium nitrate but it is very expensive to get lab grade
also requires an end user declaration here in Australia as it is classed as a drug precursor and therefore has tighter controls. I can get technical grade a lot cheaper and without the limitations but they state it isn’t food grade. Another option would be calcium nitrate. It is sold as plant fertiliser for aquariums and is a lot cheaper.

What are the risks associated with using a lower grade product.

 

[Randy Holmes-Farley Verified Community Expert]

I have chased up a source for sodium nitrate but it is very expensive to get lab grade
also requires an end user declaration here in Australia as it is classed as a drug precursor and therefore has tighter controls. I can get technical grade a lot cheaper and without the limitations but they state it isn’t food grade. Another option would be calcium nitrate. It is sold as plant fertiliser for aquariums and is a lot cheaper.

What are the risks associated with using a lower grade product.

The risks are that you do not know what the risks are with impurities in a crude product. It may be identical to the better products, just not verified to be so, or it may actually be the material that fails the higher specification testing.

Folks use cheap grades OK, but it carries a risk.

The calcium nitrate for aquaria is likely OK. It is certainly Ok if adequately pure.