Dosing phosphates?

[skuller]

Hello guys:


I am looking to start dosing phosphates, my parameters right now are:

NO3: 25ppm
PO4: Undetectable (measured with Hanna)
kH: 7.6
CA: 430

I am running a 45gal cube tank, stoked with sps mostly, 3 small fishes, so I am not sure where my Nitrates come from, I have sand but I vacuum whenever I do a WC.
I have a big skimmer and an algae scrubber, and I believe my ATS is taking out all of the PO3, and not able to take out the No3.


Is there any way to add phosphates?
Is there any DIY formula for dosing PO4s?


Thank you guys.

 

[bosshog]

I use a stock solution of 1.1g/L of trisodium phosphate. Then 1mL/100L of tank water adds 0.01ppm phosphate.

Do a search for randy Holmes Farley and tsp dosing, you should find his article.

 

[skuller]

Thank you Bosshog

If anyone have that article URL, I will be glad to have it.
Meanwhile, I will google it..

 

[bertoni]

Here's the instructions I found:

1. add 1.88g of the Trisodium Phosphate to 1 liter of water,
2. Adding 1 ml per 100 L of tank water will boost phosphate by 0.01 ppm

 

[skuller]

Here's the instructions I found:

Thank you Bertoni, that is almost double the quantity of what Bosshog said, I wonder which one is right.
However, since I want to bring them up really slow, I can start with 1.1g..and measure, I think..

 

[bertoni]

Is your product 100% trisodium phosphate?

 

[bertoni]

I double-checked the equation. It's from Randy Holmes-Farley, who is a chemist. I can provide a link via pm if you'd like.

 

[skuller]

Thank you Bertoni

That is ok, no need to provide the link, thank you very much for the information, I didn't get the product yet, will be buying that probably tomorrow and prepare the solution.

 

[bertoni]

You're welcome.

The formula is for 100% TSP.

 

[skuller]

So, I got the product.
Took 1,8 grms of it and diluted on 1L to RODI water, then dosed 2mL of that solution in my 45 Gal tank, who was 0.00 phosphates, after dosing and waited 24 hours tested with hanna and yet 0.00ppm.

The next day dosed 6mL of that solution, tested the next day and still 0.00ppm.

Also I don't see any changes in ORP, it is still at 470, I've heard that it should go down with the dosing of phosphates.


What is your advice guys? to keep dosing until I see a 0.01 mark or value?
May be I should turn off my Scrubber while dosing phosphates?

 

[bertoni]

I wouldn't expect a measurable change in ORP from dosing phosphate, not in that amount. I might try dosing up a gallon of freshly-mixed saltwater, say to 0.1 ppm or so, using the standard formula, and testing the level right away. Trying to detect a phosphate dose in a tank, especially after a day, is going to involve a lot of luck.

 

[dkeller_nc]

Yep. And even the Hanna Checkers have some degree of accuracy/precision error, and you're working at the very low end of the range.

A couple of comments about using the Hanna - it's critically important that you register the vial in the same rotation within the detector unit when you zero it with tank water as when you've added the reagent, shaken it for two minutes, then returned it to the unit for the 3 minute countdown. If you either put the vial in a different orientation from when you zeroed it, or you've put fingerprints on the side of the vial, you can easily get lots of zero readings if your phosphate's low, or really inconsistent test results.

I'm not saying this is the actual issue here - it's probable that such a low dose of phosphate is getting so rapidly consumed by algae and bacteria in your system that it pretty much disappears as soon as it hits the water. But if your test methodology isn't completely up to snuff, it will make assessing the effects of the dosing much more difficult.