Help with Titrating Rowaphos

[jbisDVM]

I’ve been using Rowaphos recently to manage phosphate in my tank and running into a weird issue. I utilize an Aquaready media reactor with both carbon and the GFO. I put the carbon on the bottom, then a layer of filter floss, followed by Rowaphos on top and then another layer of floss and the circular sponge. When I first change the media my phosphates drop to zero. But then within a week, they increase to 0.1. Once I establish that the 0.1 reading is accurate (using Hanna checker for several days in a row) I’ll change the media and start over again. I’m trying to figure out the amount of Rowaphos to use to keep levels around 0.03. But I can’t ever get there because phosphates seem to jump from 0.00 to 0.1 almost instantly, with no in between values. It’s hard to catch any values in between and I feel like I’m doing something wrong.

Any advice? How to titrate the amount of GFO to try and keep phos stable? I don’t understand the jump from zero to 0.1 with no warning in between.

 

[jbisDVM]

Things I forgot to add:
This is a 75g volume system. 65g display and a 15g sump which probably has about 10mL of water in it.
I had started with 3 tbsp of Rowaphos and gone as high as 6 tbsp but the same issue stated above keeps happening. To calculate the amount added I use the Rowaphos calculator and use 0.03 as my target to get the volume of Rowaphos to add.

 

[Randy Holmes-Farley]

There’s no calculator that can determine how much GFO is needed to stabilize a tank at a certain level. Trial and error is really the only way.

FWIW, I think 0.1 ppm phosphate is fine. Better than 0.03 ppm, in my opinion.

This has more:

Randy’s Thoughts on Nutrient Target Ranges

Thoughts on Nutrient Target Ranges by Randy Holmes-Farley Almost nothing in the world of reef aquarium chemistry causes as much discussion as selecting and maintaining ranges for nitrate and phosphate. Some aquarists want low targets, some want...

www.reef2reef.com

 

[jbisDVM]

There’s no calculator that can determine how much GFO is needed to stabilize a tank at a certain level. Trial and error is really the only way.

FWIW, I think 0.1 ppm phosphate is fine. Better than 0.03 ppm, in my opinion.

This has more:

Randy’s Thoughts on Nutrient Target Ranges

Thoughts on Nutrient Target Ranges by Randy Holmes-Farley Almost nothing in the world of reef aquarium chemistry causes as much discussion as selecting and maintaining ranges for nitrate and phosphate. Some aquarists want low targets, some want...

www.reef2reef.com

Appreciate this Randy, thank you. I read this and it puts a lot in perspective.

One of my thoughts above though was why does my phosphate seem to jump from 0 straight to 0.1 with no in-between? If my input is the same regarding food and feeding habits, why isn’t the accumulation a slow slope upward? It makes me wonder if my Hanna checker is accurate or if there’s a reason these two numbers are all I’m getting lately.

 

[gbroadbridge]

Appreciate this Randy, thank you. I read this and it puts a lot in perspective.

One of my thoughts above though was why does my phosphate seem to jump from 0 straight to 0.1 with no in-between? If my input is the same regarding food and feeding habits, why isn’t the accumulation a slow slope upward? It makes me wonder if my Hanna checker is accurate or if there’s a reason these two numbers are all I’m getting lately.

There's nothing magical about Rowaphos except for the marketing.
It's just GFO.

When I use GFO I'd normally use 150-200 grams (75 gal tank).

If you wish to drop to 0.03 (not really necessary, but I sat at that level for a few years) just use more GFO so it last longer.

I'd expect that once the GFO is exhausted the tank Phosphate level could rise quite quickly.