How to mix Sodium Nitrate& Potassium Phosphate

[t5Nitro]

The math doesn't add up that way if using that plantedtank link above. If 0.25tsp = 0.25g and I mixed it into 100mL tank water and added it fully to 75 gallons I should have raised the phos 1ppm, unless I'm missing another factor. If anything I guess I know that a full 100mL with 0.25tsp will raise it approximately 0.5ppm and I should probably dose no more than 10mL of that concentration at a time to reach 0.05ppm, lol.

 

[Shirak]

The link? Isn't that for potassium phosphate? I thought you were using trisodium phosphate. My total water volume is about 75 gallons and I dose 21ml/day from a stock solution of .196g into 420ml water to raise my PO4 .02ppm.

 

[Shirak]

These are the calculations I am using. Maybe Randy can confirm if I am doing these correctly. My last chemistry class was a looong time ago.

Molecular weight of Na3PO4 163.94
Molecular weight of PO4 94.971

163.94/94.971 = 1.73 g/L to make 1000ppm solution

To add 1000ppm to 283.9L (75gallons) 283.9L x 1.73g = 491.147g
to add .02ppm 491.147 x .00002 = .00982g

Since the water volume is the same you can do the calculation figure what you put in if you raised 75 gallons by .5ppm
491.147 x .0005 = .246 grams

 

[t5Nitro]

I've an advanced degree but can't do chemistry math. I tried to figure out how much I dosed the tank in weight by X mg into 284L of water to equal 0.5 mg/L. Some cross multiplying gave me 0.142g that I threw in there to raise it but I suppose it doesn't mean much if I don't have a scale. As I look down at this full sheet of paper full of scribbles.

Appreciate the assistance. Since our tanks are similar I may just go ahead and make the same concentration you're using.

 

[Randy Holmes-Farley]

What calculator?

A quarter teaspoon might weigh 1.25 gram and contain 0.7 gram (700 mg) phosphate (very roughly).

Add that too 70 gallons (265 L) and the concentration is 700 mg/265 L --> 2.6 ppm.

A big dose.

 

[Randy Holmes-Farley]

Here's a calculator. Use the entry for potassium phosphate and use 2/3 as much since sodium weighs less than potassium.

James' Planted Tank - Dosing Calculator

 

[dieselkeeper]

I used the above calculator to raise my phosphates in a 220 gal. A bit of advice, read carefully. I mixed 15 grams of mono potassium phosphate in 500 ml of water. I added 100 ml each day for 3 days. I use a Hanna ULR phosphate tester. The water to be tested turned a darkest blue. It tested at blinking 2.5 meg/l. Which is out of range for the tester. Reading the dosing instructions again, I was suppose to dose 1 ml to raise phosphates 0.03 meg/l. A 30 gal water change did not lower phosphates below 2.5 meg/l. So I broke out the GFO. Yesterday afternoon it was 1.65 meg/l. I'm hoping it is at a level close to 0.05 meg/l this morning. My tank is 6 years old and I'm having to dose nitrates and phosphates. Both go to zero after dosing a small amount. A reef tank definitely keeps me on my toes lately.

 

[Shirak]

If it helps I was using the formulas and calculations on this web page. Seems to work out ok on my tank. I do test every few days or so just to keep track. I find the bigger issues right now is trying to keep the refugium from overgrowing and then stripping it clean. My tank is also kinda in flux... I decided to do the fallow route and to catch all the fish I pulled all the rock.. so I have a bed of sand and corals stuck all over lol. It was fairly new so the load is light on the system.
molecular weight/ppm conversions

 

[t5Nitro]

What calculator?

A quarter teaspoon might weigh 1.25 gram and contain 0.7 gram (700 mg) phosphate (very roughly).

Add that too 70 gallons (265 L) and the concentration is 700 mg/265 L --> 2.6 ppm.

A big dose.

It's hard to say what I actually dosed with since even with that estimated weight which seems reasonable that I raised my tank 1/5th of that estimated rise of 2.6ppm. Maybe the measuring 1/4tsp is far from an accurate 1/4tsp. I rechecked today with it being 0.18 ppm (0.56ppm about an hour after dosing yesterday - also odd, I thought my hanna ULR only goes to 200ppb, or 0.2ppm). In any case it looks like it's on the downtrend and will be within normal limits tomorrow. If anything, I think I can use the same measuring spoon and dilute it further 6x into 600mL of water, and dosing 5mL of that Xmg/0.6L stock solution should raise my tank by 0.018 ppm, at least based on the 0.56ppm I got with the initial dose. Interesting nonetheless. A scale would solve that mystery!

 

[Randy Holmes-Farley]

It's hard to say what I actually dosed with since even with that estimated weight which seems reasonable that I raised my tank 1/5th of that estimated rise of 2.6ppm. Maybe the measuring 1/4tsp is far from an accurate 1/4tsp. I rechecked today with it being 0.18 ppm (0.56ppm about an hour after dosing yesterday - also odd, I thought my hanna ULR only goes to 200ppm, or 0.2ppm). In any case it looks like it's on the downtrend and will be within normal limits tomorrow. If anything, I think I can use the same measuring spoon and dilute it further 6x into 600mL of water, and dosing 5mL of that Xmg/600mL stock solution should raise my tank by 0.018 ppm, at least based on the 0.56ppm I got with the initial dose. Interesting nonetheless. A scale would solve that mystery!

What you dose to a tank and what you see can be vastly different when dosing phosphate. Lots of it binds to rock and sand. One member showed in a test tank tha he had to dose many ppm before retaining 0.1 ppm phosphate in solution.

The calculation is a very rough guide.