Adding PO4 to ATO for dosing

[Necrodaemus]

I’m struggling with keeping PO4 up on my tank. It consistently reads at 1ppb (0.003ppm) with a Hanna Phosphorus ULR and I’ve been manually dosing it daily to help maintain it. Feeding heavy doesn’t help much and I can’t add any more fish to this tank. Could anyone that has used it in an ATO explain how much to add to the water so that it provides a steady, consistent dosing to help maintain 0.03?

 

[Randy Holmes-Farley Verified Community Expert]

I’m struggling with keeping PO4 up on my tank. It consistently reads at 1ppb (0.003ppm) with a Hanna Phosphorus ULR and I’ve been manually dosing it daily to help maintain it. Feeding heavy doesn’t help much and I can’t add any more fish to this tank. Could anyone that has used it in an ATO explain how much to add to the water so that it provides a steady, consistent dosing to help maintain 0.03?

Definitely not. We can calculate how much to dose to have dosed a particular amount, but what happens to it after it’s in the tank varies tremendously.

 

[Randy Holmes-Farley Verified Community Expert]

I’ll note that if you mean 1 ppb phosphorus, you have about 0.01 phosphate, and with the specs of the device, it could easily be above 0.01 ppm.

 

[Necrodaemus]

Definitely not. We can calculate how much to dose to have dosed a particular amount, but what happens to it after it’s in the tank varies tremendously.

That’s what I expected. It’s the further dilution once it hits the sump/DT that leaves me scratching my head. IE, I could add enough to the ATO to equal 0.03ppm but once that small amount of water from the ATO is pumped into the DT, I suspect it will be such a small, diluted amount that it’s not going to help much.

 

[Necrodaemus]

I’ll note that if you mean 1 ppb phosphorus, you have about 0.01 phosphate, and with the specs of the device, it could easily be above 0.01 ppm.

I’m using the Hanna Phosphorus ULR checker and unless my conversion is off, 1ppb equals 0.003 ppm of actual PO4

 

[Randy Holmes-Farley Verified Community Expert]

That’s what I expected. It’s the further dilution once it hits the sump/DT that leaves me scratching my head. IE, I could add enough to the ATO to equal 0.03ppm but once that small amount of water from the ATO is pumped into the DT, I suspect it will be such a small, diluted amount that it’s not going to help much.

Dilution is easy to calculate. Consumption by various processes, including binding to rock and sand, is not.

 

[Randy Holmes-Farley Verified Community Expert]

I’m using the Hanna Phosphorus ULR checker and unless my conversion is off, 1ppb equals 0.003 ppm of actual PO4

Yes, sorry, you are correct, but the claimed accuracy is +/- 5 ppb, so phosphate could be as high as 0.018 ppm.