Help with using Rowaphos

[ReefDreamz]

I have been using Rowaphos for a few months now and it doesn't seem to be working very well.

Am I using it correctly?

I am using it in a fluidised reactor with the top layer just barely moving. Twice a week I measure PO4 using a Hanna ULR Phosphate tester. Once a week I use this calculator: http://www.rowaphos-calculator.com/ plug in my result (for example today it was 0.11) and plug in 0.05 as the desired phosphate level. Then I take the recommended amount to add in oz and convert it to grams.

Example:

I then add that amount of Rowaphos in grams (47.9 grams in this example) to my reactor, rinse with a bit fresh salt water and add the reactor back to my sump. I have been adding the new Rowaphos on top of the existing Rowaphos in the reactor, not emptying the reactor then adding the new. I do empty the reactor completely about every 4 weeks and start over. Should I be emptying it every time I add new (weekly)? Should I be testing and adding new Rowaphos more often than once a week?

It's not really working that well. My PO4 rarely gets below 0.1 even though I'm using 0.05 as the desired level in the calculator. Here is my last 4 months of PO4 readings:

 

[blaxsun]

You want to change out your Rowaphos every 1-2 months, ie: completely replace. This may not resolve your issues, but your phosphate levels are actually fine (0.10-0.15 is an ideal range).

 

[Randy Holmes-Farley Verified Community Expert]

I have been using Rowaphos for a few months now and it doesn't seem to be working very well.

Am I using it correctly?

I am using it in a fluidised reactor with the top layer just barely moving. Twice a week I measure PO4 using a Hanna ULR Phosphate tester. Once a week I use this calculator: http://www.rowaphos-calculator.com/ plug in my result (for example today it was 0.11) and plug in 0.05 as the desired phosphate level. Then I take the recommended amount to add in oz and convert it to grams.

Example:

I then add that amount of Rowaphos in grams (47.9 grams in this example) to my reactor, rinse with a bit fresh salt water and add the reactor back to my sump. I have been adding the new Rowaphos on top of the existing Rowaphos in the reactor, not emptying the reactor then adding the new. I do empty the reactor completely about every 4 weeks and start over. Should I be emptying it every time I add new (weekly)? Should I be testing and adding new Rowaphos more often than once a week?

It's not really working that well. My PO4 rarely gets below 0.1 even though I'm using 0.05 as the desired level in the calculator. Here is my last 4 months of PO4 readings:

Calculators are pretty much useless for phosphate reduction for at least three reasons:

1. You do not want to drop phosphate too fast, and an all at once calculation (if it were possible) can do that too fast.

2. There is a lot of phosphate bound to rock and sand that needs to be slowly stripped off if you want to attain a steady and lower phosphate concentration. Thus it will take much more GFO and much longer than one might expect to reach a new, lower stable reading.

3. I have zero confidence that such a calculator understands how much phosphate binds to GFO at any given phosphate concentration in the water. This relationship is not really amenable to devising a calculator without doing a lot of experimental work and fitting some complex binding curve to the observed data.