PO4 and RODI water

[bigyankfan]

I am having trouble getting my PO4 levels below 0.1 (I am using the Milwaukee Low PO4 meter) - I have been doing regular water changes and I do not overfeeed. I do not have an algae problem but my SPS are brwoning out. I run a GFO reactor but still no luck so I tried to test the PO4 levels in my RODI water and I got a reading of 0.09. Here is the thing - my TDS meter shows a reading of 0. What's going on? Any and all suggestions welcome.

 

[Boomer]

First thing Yank is it the meter. Try testing it against a test kit or some distilled water.

 

[fjpod]

You pose a good question. Do phosphates show up on a TDS meter?

 

[mbg75]

Tds meter is a conductivity meter. If its not conducive, it won't show up as a reading.

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[bigyankfan]

I don't understand - are phosphates conductive or not?

Tds meter is a conductivity meter. If its not conducive, it won't show up as a reading.

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[andylee]

They should be. What are units for the phosphate test? The TDS meter goes by PPM, right? If phosphates are also PPM and only 0.09, they might be below the range of the TDS meter.

 

[bigyankfan]

They should be. What are units for the phosphate test? The TDS meter goes by PPM, right? If phosphates are also PPM and only 0.09, they might be below the range of the TDS meter.

That's a good point - I will check when i get home. I am also going to buy some distilled water on the way home and use the Milwaukee PO4 meter on that and see what I get. Thx everybody.

 

[bigyankfan]

The Milwaukee meter's display is mg/L and I think the TDS meter is PPM - I have no idea how to convert from one to another.

 

[Widdy]

The Milwaukee meter's display is mg/L and I think the TDS meter is PPM - I have no idea how to convert from one to another.

I believe it's a 1:1 correspondence, Eric.

 

[andylee]

I don't remember either. Something involving molecular weights and Avogadro's number!

 

[fjpod]

I would think what matters is whether phosphates are considered a dissolved solid. I know that if I test my tap water, I measure a significant amount of phosphates with a test kit. If I run the water through my DI unit, it measures negligible phosphates. MY TDS also measures zero after filtration, but one cannot assume that if TDS is zero, that phosphates are also.

 

[bigyankfan]

I just used my PO4 meter on distilled water and got a reading of 0.00 - now what? If I change the filters in my RODI unit, will the phosphates in the output drop to zero?

 

[kasha]

The amount of phosphate you are adding in your ro di is negligible compared to feeding and fish wast, even if your reading 0.09 ppm. You are probably adding x100 with each feeding. You need a better export mechanism. Either change out your gfo more frequently, fuge or organic carbon dosing.

Or


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[bigyankfan]

I just changed out my GFO and carbon and I switched to the new PO4X4 GFO. Maybe I am not using enough - I tried to figure out how much to use for a 120G tank and I put 7 teaspoons in the reactor. I don't know if I should more GFO and try that.

 

[Boomer]

are phosphates conductive or not?

Yes, they are quite conductive with a charge of neg 3. When dealing with ultra pure water measuring issues can arise on meters and probes.



I just used my PO4 meter on distilled water and got a reading of 0.00

Good and what was the TDS of that DW ? I want to see:

1. TDS of DW
2.TDS of tap water and PO4
3. TDS of RO and PO4
4. TDS of fresh new RO/DI and PO4 dripped into a clean glass and not taken for a storage container, which might be contaminated.




If phosphates are also PPM and only 0.09, they might be below the range of the TDS meter.

Range of the meter is down to 0.04 with a +/- accuracy if 0.04. Meaning, if the meter reads say .08 the actual PO4 is or may be somewhere between .04 - 0.12 ppm.


I believe it's a 1:1 correspondence

Yes, /say


mg /l = PPM x Density ( NOT specific gravity)

Since D of FW is 1 then ppm = mg /l




0.09

1. That may or may not be a meter issue. RO/DI is ultra pure water and some meters, probe and kits have issues with this type of water just like some do in seawater. The DW reads 0 ppm PO4 but what would the PO4 read in RO/DI with a grain or two of table salt in it.

2. Could the reading really be from where this water is stored ? Take a fresh sample right out of the DI and drip into a clean glass and then see what it reads. Take a sample of your water and get a reagent from PO4 kit and see if the water turns blue when you add it.

3. I do not buy the DI is shot when you get a TDS of 0 ppm and ONLY PO4 is leaking through according to you tests.


IMHO it is #1, a false reading

 

[Forreal]

Po4

what do you store your RO water in? some plastics are known to have phosphates leak out into the water.