Confused by Rowaphos

griff500

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I've been using Rowaphos in a Phosban reactor. It appears to be fluidised correctly and it's not my first time using this type of setup.

Phosphate levels do not particularly appear to be dropping and after 24 hours the measure output is actually higher than the display level, which matches the sump level, measured multiple times and getting fairly consistent results.

Does anyone have any ideas what could cause the output from the reactor to be higher than the level in the display and sump? I can understand output being the same as input to the reactor if the media is spent but this consistently measures higher.
 
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griff500

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Hi Randy.

It's varying between 0.1 and 0.15. I understand it can be depleted fast and that phosphate gets stored up in sand and rock and released but what's confusing me is that the output is significantly higher than the input - last measurement was about 0.22 output with the display and sump both measuring 0.15 (it had been 0.1 yesterday).

I didn't think that Rowaphos released the phosphate that it had absorbed?
 

Randy Holmes-Farley

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I didn't think that Rowaphos released the phosphate that it had absorbed?

It will, if it is absorbed to capacity/equilibrium at a higher phosphate level and you somehow lower it in the water.

The phosphate just comes to on/off equilibrium binding with the GFO surface, and the higher the phosphate in the water, the more binds.

How long has this batch been in the water?
 

Greenstreet.1

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I use it also never noticed that will test my output in a minute and see what I get. Last test on Dt I was at 0.03 after feeding.
 

Greenstreet.1

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Dt=0.03
Reactor =0.02

1cup of rowa in reactor been in there for about 6wks now soon time for change.
 
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griff500

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You have less to remove than me of course and test kits have a certain degree of inaccuracy.

I'm going to assume that the Rowa was spent and releasing what it had previously bound. I'll also try lowering the flow to the bare minimum required to keep it tumbling and see if that helps. It's probably going to cost a small fortune on Rowa to get all of the phosphate out of the rocks and sand...
 

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Before adding the rowa to the tank I was dosing about 6 drops a day of po4 Rx to knock down the po4 in the tank it helped me a lot started back the rowa for better control.
 
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griff500

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Every product description for Rowaphos states that it will absolutely NOT release phosphate. If that is true then how could I possible get a higher reading from the output than from the water going into the reactor?

It doesn't particularly seem to be making a dent at the moment and I have never seen a zero reading from the output - at best just a little bit below the input. I did use an aluminium-based product a while ago and it seemed to be more effective, yet I thought Rowaphos was supposed to be more aggressive.

Still confused.
 

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Every product description for Rowaphos states that it will absolutely NOT release phosphate. If that is true then how could I possible get a higher reading from the output than from the water going into the reactor?

It doesn't particularly seem to be making a dent at the moment and I have never seen a zero reading from the output - at best just a little bit below the input. I did use an aluminium-based product a while ago and it seemed to be more effective, yet I thought Rowaphos was supposed to be more aggressive.

Still confused.

Take a look at this

ROWAPHOS amounts
https://www.reef2reef.com/index.php?threads/ROWAPHOS-amounts.390099/
 
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griff500

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I see. I appreciate your efforts but my question isn't about how much to use.

What confuses me is that I test the output of the reactor and never see zero or even close to it. Sometimes it reads higher than the level in the tank or sump, even though they say it will not release phosphate. These are the two things that I find odd.

Corals are improving and growing and algae growth is a bit weaker so it's doing something but I find the effluent readings strange.
 

Randy Holmes-Farley

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Every product description for Rowaphos states that it will absolutely NOT release phosphate..

Which is just so wrong. lol

It is easy to determine for yourself, and I have, even knowing what the outcome would be. The binding is certainly reversible.

Let GFO (any brand) equilibrate in 2 ppm phosphate solution (2 ppm still in the water after binding).

Take off all the liquid, and maybe even rinse the solids quickly. Put them back in fresh seawater. Low and behold, phosphate rises.

Of course it does. This is perfectly well understood by scientists like myself who are experts in surface chemistry and/or the binding of phosphate to materials.

It won't release it if the concentration in the water never drops lower than the concentration it was adsorbed from. That is debatable, depending on what is in the water, but is likely the nugget of truth behind the broad sweeping and incorrect generalization they use for advertising.
 

Randy Holmes-Farley

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I see. I appreciate your efforts but my question isn't about how much to use.

What confuses me is that I test the output of the reactor and never see zero or even close to it. Sometimes it reads higher than the level in the tank or sump, even though they say it will not release phosphate. These are the two things that I find odd.

Corals are improving and growing and algae growth is a bit weaker so it's doing something but I find the effluent readings strange.

I suspect testing error is part of the issue. Some folks find testing the same water over and over gives varying results.
 
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griff500

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I’m not convinced about testing error as I get fairly consistent results and the difference between output and input can be significant. Perhaps it’s just a reflection of how much has been bound up in the rock and sand.
 

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I’m not convinced about testing error as I get fairly consistent results and the difference between output and input can be significant. Perhaps it’s just a reflection of how much has been bound up in the rock and sand.

That's a possibility. Anything that lowers the bulk water phosphate value below the equivalent concentration bound to the media (any type) will allow phosphate to desorb.
 
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griff500

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With tank measurements varying from 0.1 to 0.18 (yes, that wide a variation, although some of that variation could be test accuracy - let's say an average of 0.14), should Rowaphos be exhausted within hours? Is it ok to use double the amount for a while or would smaller amounts be better. I cannot change it every few hours..
 

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With tank measurements varying from 0.1 to 0.18 (yes, that wide a variation, although some of that variation could be test accuracy - let's say an average of 0.14), should Rowaphos be exhausted within hours? Is it ok to use double the amount for a while or would smaller amounts be better. I cannot change it every few hours..

Depends on the flow through it, but I wouldn't guess it would be hours in a typical setup. Might a a day or two.
 
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