DIY phosphate please double check my math

[FishTacos2]

I know there are posts on this but I would like someone to check my math as there is obviously a lot on the line if I mess this up.

I want to make a 1000ppm batch of trisodiumphosphate, which is I believe is what I’m currently buying premade for $20 per bottle from a popular company.

1000ppm= 1g/l

This divided by 58% phosphate by weight is 1.7g

So I’m making 500ml batch so 0.85g in 500ml

This seems like almost nothing (pic)

3 cc should raise my phosphate by 0.01 in 80 gallons

It also seems strange to be using TSP which is used as a household cleaner.

All of this Correct?

 

[Oldsman]

@Miami Reef

 

[Randy Holmes-Farley Verified Community Expert]

What material exactly? Is it a hydrate? (Impacts the calculation). I recommend food grade sodium phosphate.

 

[Miami Reef]

What material exactly? Is it a hydrate? (Impacts the calculation). I recommend food grade sodium phosphate.

The sodium phosphate dibasic I purchased has no mention of the hydrate.

Would you assume it’s dihydrate?

 

[Randy Holmes-Farley Verified Community Expert]

The sodium phosphate dibasic I purchased has no mention of the hydrate.

Would you assume it’s dihydrate?

No, I would assume that is anhydrous.

But the one I am using from Amazon (sodium phosphate tribasic dodecahydrate) definitely does have a lot.

 

[Randy Holmes-Farley Verified Community Expert]

In the end, exactness in this context may be nearly meaningless since everyone will titrate the doses they need based on testing, and an unknown but potentially large fraction will bind to rock and sand when added to a normal reef tank.

 

[Miami Reef]

No, I would assume that is anhydrous.

But the one I am using from Amazon (sodium phosphate tribasic dodecahydrate) definitely does have a lot.

Thanks. My recipe for sodium phosphate dibasic used the anhydrous form. Na2HPO4

I just mentioned that tribasic and monobasic are similar enough to use interchangeably, especially after accounting for rock adsorption.

 

[Miami Reef]

This is the recipe for dibasic

Dissolve 3 g of Sodium Phosphate Dibasic (Na₂HPO₄) in 1 L of freshwater.


Dose 1 mL per 100 L to raise PO₄ by 0.02 ppm.

DIY Phosphate Dosing Recipe

Sometimes phosphate can be so stubbornly low that the only way to meaningfully raise it is by directly dosing phosphate. When you feed foods, you’re adding nitrogen, carbon, and loads of organics. This effect is compounded if you’re trying to offset rocks that initially work against you by...

www.reef2reef.com

 

[FishTacos2]

What material exactly? Is it a hydrate? (Impacts the calculation). I recommend food grade sodium phosphate.

This is what I purchased

 

[Miami Reef]

This is what I purchased

Yes.

If you follow the recipe linked above, using trisodium phosphate instead of dibasic, it will actually raise your PO₄ by about 0.017 ppm per 0.02 ppm dose. The difference is minor and the two are effectively interchangeable.

Trisodium phosphate delivers 86.6% as much phosphate per gram as dibasic.