Disodium Phosphate dosing calculator?

[fishbox]

Anyone have a good dosing calculator for raising Po4 using Disodium Phosphate? All the calculators that I've run across are based on using Potassium Phosphate.

 

[Art2249]

yea me too. I just mixed some up. I kind of just winged it and dosed a tiny bit. I mixed 1 tsp into 3 1/8 cup ro water and dosed .25 ml into 12 gallons. Still no reading. So I just dosed .5 ml and will test again tomorrow.

 

[fishbox]

yea me too. I just mixed some up. I kind of just winged it and dosed a tiny bit. I mixed 1 tsp into 3 1/8 cup ro water and dosed .25 ml into 12 gallons. Still no reading. So I just dosed .5 ml and will test again tomorrow.

Please keep me posted

 

[Gareth elliott]

I use dipotassium phosphate for my planted aquaria. Which is a similar salt.

I use roughly 100l of water .029g of kh2po4.
Each ml of solution then provides .2ppm po4
I use a jewlers scale to get the 1/1000 of a gram measurement.

 

[Art2249]

I saw somewhere you can mix it up like trisodium phosphate, which I did see a thread for, but when using disodium phosphate you dont use as much. There was a multiplier like .8 something. I know jack about chemistry though so don't listen to me.

 

[fishbox]

Where's the man when you need him
@Randy Holmes-Farley

 

[dragon99]

From this thread as a reference, https://www.reef2reef.com/threads/dosing-monosodium-phosphate.314502/

Na2HPO4 - 141.96 g/mol, PO4 - 96 g/mol
So each g is ~67% PO4.

If you add 3g Na2HPO4 to 1L RODI, you will have a stock solution of 2mg/mL

Convert your tanks water volume to liters, and then determine the dosage from there. Example, if you have a 100L tank, and add 1ml, would have added .02 mg/ml, or .019 ppm PO4

Someone should definitely check my math though, I haven't finished my coffee.

 

[Randy Holmes-Farley Verified Community Expert]

When using calculators for phosphate, beware that sometimes they do not distinguish the different forms. E.g., Na3PO4 vs Na2HPO4 vs NaH2PO4. They may call them all sodium phosphate.

That said, dosing phosphate to a reef cannot be exact anyway since some (often most of it) of it is going to bind to rocks and sand if you are trying to raise levels. So you will usually need a lot more than you calculate.

Try using this calculator:

http://www.theplantedtank.co.uk/calculator.htm

and pick the entry for potassium phosphate. It is assuming that means KH2PO4.
It turns out that entry is almost exactly correct for Na2HPO4 (disodium phosphate; it is only off by 4.4%, which is insignificant for our purposes).

 

[DiZASTiX]

When using calculators for phosphate, beware that sometimes they do not distinguish the different forms. E.g., Na3PO4 vs Na2HPO4 vs NaH2PO4. They may call them all sodium phosphate.

That said, dosing phosphate to a reef cannot be exact anyway since some (often most of it) of it is going to bind to rocks and sand if you are trying to raise levels. So you will usually need a lot more than you calculate.

Try using this calculator:

http://www.theplantedtank.co.uk/calculator.htm

and pick the entry for potassium phosphate. It is assuming that means KH2PO4.
It turns out that entry is almost exactly correct for Na2HPO4 (disodium phosphate; it is only off by 4.4%, which is insignificant for our purposes).

I followed these instructions, and I understand that "some / often most" will bind to rocks and sand. However, I've noticed I've been able to get up to 0.13 ppm phosphate, only to have it drop to 0 within an hour or so. I assume this is the binding to rocks and sand and absolutely not a consequence of either carbon dosing or algae turf scrubber, correct?

Also, is there a way to guesstimate how much I need to get a measurable reading? I'm just trying to get 0.04 ppm max, so I concocted a mixture that will produce 0.01 ppm per 1 mL added, and I add 4 mL at a time and use the Hanna Checker to measure (and test 0.00 ppm except when testing soon after dosing).

 

[Randy Holmes-Farley Verified Community Expert]

It can be all of those explanations, but rock binding alone can take many whole ppm down to 0.1 ppm. So it is a big effect.

There’s no way to calculate since every tank will have a different amount of exposed calcium carbonate surfaces.

 

[DiZASTiX]

It can be all of those explanations, but rock binding alone can take many whole ppm down to 0.1 ppm. So it is a big effect.

There’s no way to calculate since every tank will have a different amount of exposed calcium carbonate surfaces.

Thank you for the information. After pouring in around 50 mL of my concoction, I was able to finally produce 0.03 ppm phosphate reading. In theory, in a vacuum, I would've produced a reading of 50 ppm phosphate!!

 

[DiZASTiX]

Boy you're spot on, Randy. A few hours ago, all phosphate has vanished. If only people with phosphate issues can experience the sort of magic I'm experiencing. Anyway, I'm reading 0.00 again on the Hanna Checker ULR, and so with an accurate syringe, I put in 4 mL of my concoction, then said what the **** to myself, and poured a good swig into the aquarium.

 

[Lasse]

IMO - be carefully - at the moment you are filling up all of your reservoirs of PO4. when they are filled up - you can´t use the dosing you use at the moment. IMO - if you start to read some P or PO4 - you are close to the max of the reservoirs.

Sincerely Lasse

 

[DiZASTiX]

IMO - be carefully - at the moment you are filling up all of your reservoirs of PO4. when they are filled up - you can´t use the dosing you use at the moment. IMO - if you start to read some P or PO4 - you are close to the max of the reservoirs.

Sincerely Lasse

So what you are saying, @Lasse , is that I'm coming close to the point at which I'll have PO4 in my system?

 

[DiZASTiX]

So what you are saying, @Lasse , is that I'm coming close to the point at which I'll have PO4 in my system?

Yikes .. 0.39 ppm PO4 on the Hanna Checker. Granted, it's only been a bit of time. Hopefully this will come back down.

I'm guessing 0.39 ppm PO4 is way too high for any system, much less ULNS?

 

[Lasse]

In a living system - there is a lot of reservoirs for P. Bound to substrate through metal bondings, bound in decaying organic matters and some more ways. When you for a long time run with an aggressive P removing methodology you will empty the reservoirs through equilibrium processes and when you start adding P again - the reservoirs will be filled up. Fill up a glass with water with a constant stream of water and you will understand what I mean. This mean that when you reach "the spill over point" - you should only add the amount that is normal used by you system. I use to try to balance between 0.04 and 0.1 as PO4. if I do that - I know there is reservoirs still in the system - fixing the P if my equipment fail or the need for P increases. If I read 0 - I know that my reservoirs are consumed

Do not panic - just apply your normal methods for taking away P from your system. GFO or AL based media. Panic will do more harm than the actually content - take a beer and take it with equanimity - The forbidden s-t word just happens now and then

Sincerely Lasse

 

[DiZASTiX]

In a living system - there is a lot of reservoirs for P. Bound to substrate through metal bondings, bound in decaying organic matters and some more ways. When you for a long time run with an aggressive P removing methodology you will empty the reservoirs through equilibrium processes and when you start adding P again - the reservoirs will be filled up. Fill up a glass with water with a constant stream of water and you will understand what I mean. This mean that when you reach "the spill over point" - you should only add the amount that is normal used by you system. I use to try to balance between 0.04 and 0.1 as PO4. if I do that - I know there is reservoirs still in the system - fixing the P if my equipment fail or the need for P increases. If I read 0 - I know that my reservoirs are consumed

Do not panic - just apply your normal methods for taking away P from your system. GFO or AL based media. Panic will do more harm than the actually content - take a beer and take it with equanimity - The forbidden s-t word just happens now and then

Sincerely Lasse

Thank you for the helpful advice, @Lasse . I went to bed, woke up 6-7 hours later, and phosphate had "dropped" from 0.39 ppm to 0.10 ppm (tested by Hanna Checker ULR). I think even perhaps without GFO, it might keep going down, no? Also, is 0.1 ppm seemingly a safe range to let it fall naturally (e.g., my carbon dosing and algae turf scrubbing?

 

[Lasse]

Thank you for the helpful advice, @Lasse . Also, is 0.1 ppm seemingly a safe range to let it fall naturally (e.g., my carbon dosing and algae turf scrubbing?

Depend of whom you ask You can see in my build tread how my tank looks like. I run between 0.1 to 0.04 - sometimes up to 0.15 as ppm PO4. NO3 around 1 - 15 ppm - goal 4-5 ppm. In the first page of my build tread - there is a video of my old tank. At that time - it had 2.14 as PO4 and NO3 - who knows - never measured.

No panic - let i be and measure tonight just before the light leave their max.

Sincerely Lasse

 

[EJReef]

Depend of whom you ask You can see in my build tread how my tank looks like. I run between 0.1 to 0.04 - sometimes up to 0.15 as ppm PO4. NO3 around 1 - 15 ppm - goal 4-5 ppm. In the first page of my build tread - there is a video of my old tank. At that time - it had 2.14 as PO4 and NO3 - who knows - never measured.

No panic - let i be and measure tonight just before the light leave their max.

Sincerely Lasse

Is there any need to worry if it keeps reading 0 on a Hanna ULR? I feed quite a bit and it always reads 0 but i have 3ppm nitrate.

 

[Lasse]

Once again - depend of whom you ask - IMO - it is more problematic than reading steady 0.1 ppm or even higher

Sincerely Lasse