ROWAPHOS amounts

Joe Batt · May 12, 2018

The amount to add of ROWAPHOS is pretty hard to tie down, various articles give different advice.

Does the amount added directly follow the rate of removal? ie If you add twice as much will the levels reduce twice as fast or will it just take longer to deplete?

Randy Holmes-Farley · May 12, 2018

The exact answer on rates depends on how you use it. If used in a reactor where there is a lot of phosphate going in and little coming out, then doubling the amount may only make it last longer and reduce the amount in the effluent slightly.

But in general, overshooting is a risk and its best to start slow.

SPR1968 · May 12, 2018

Joe Batt said:
The amount to add of ROWAPHOS is pretty hard to tie down, various articles give different advice.

Does the amount added directly follow the rate of removal? ie If you add twice as much will the levels reduce twice as fast or will it just take longer to deplete?

It depends on the phosphate level. If you have high phosphate more Rhowaphos in a reactor for example, will strip it out faster. If your Phosphate is low, it will last a lot longer between changes.

It’s has a capacity to remove a certain amount of phosphate

So 100ml of Rhowaphos will remove 3ppm phosphate from 105 USG of saltwater.

Randy Holmes-Farley · May 12, 2018

SPR1968 said:
It’s has a capacity to remove a certain amount of phosphate

So 100ml of Rhowaphos will remove 3ppm phosphate from 105 USG of saltwater.

Where did that number come from?

SPR1968 · May 12, 2018

Randy Holmes-Farley said:
Where did that number come from?

Here you go

https://www.theaquariumsolution.com/product/17/96

Randy Holmes-Farley · May 12, 2018

SPR1968 said:
Here you go

https://www.theaquariumsolution.com/product/17/96

I don't believe that such a number is useful, or an appropriate way to think about phosphate binding. It' is also misleading.

As you can see from figure 2 from their own data in this pdf from that page, the amount bound is very strongly a function of the phosphate concentration, and also whether they are talking about salt or fresh water.

https://www.theaquariumsolution.com/sites/default/files/downloads/Rowaphos Test Report .pdf

At 0.03 ppm phosphate (= 10 ug/L P; many people's goal), it is binding much, much less than at higher phosphate values. Probably much less than 1/10th as much.

So one expects far, far less capacity at lower phosphate levels than at higher levels.

Randy Holmes-Farley · May 12, 2018

Their table 4 and Figure 2 in that link allows one to determine how much phosphate is bound at reasonable target levels.

From Figure 2, I estimate that at 0.03 ppm phosphate (10 ug/L P) Rowaphos binds about 1 mg of P per gram of dry material.

From table 4, the dry bulk density is 560 g/L.

So the 100 mL of material that you referenced contains 56 grams of dry GFO, and that 56 grams will bind about 56 mg of P (172 mg of phosphate).

In the 105 gallons (400 liters) that you/they mentioned, it will then bind about 172 mg/400 L = 0.43 mg/L (not the 3 mg/L (ppm) they mention). At higher phosphate concentrations it binds more, but unless you maintain the level higher, you won't use that capacity.

Moral of the story: don't accept hobby chemical company claims without seeing how they arrived at it and if it makes sense. They often do not.

Joe Batt · May 12, 2018

The tank is still only FOWLR with the cycle having completed about a month ago. I had a large algae bloom that lasted around 2 weeks and the PO4 was very low at that stage but now that has gone the PO4 has crept up again (I understand why and the process) I am wanting to get the PO4 and a few problem metals that showed up in the ICP tests down before I add any corals. I am thus not really concerned at the moment about the rate I reduce the PO4 since it shouldn't affect anything.

Randy Holmes-Farley · May 12, 2018

Joe Batt said:
The tank is still only FOWLR with the cycle having completed about a month ago. I had a large algae bloom that lasted around 2 weeks and the PO4 was very low at that stage but now that has gone the PO4 has crept up again (I understand why and the process) I am wanting to get the PO4 and a few problem metals that showed up in the ICP tests down before I add any corals. I am thus not really concerned at the moment about the rate I reduce the PO4 since it shouldn't affect anything.

Which other metals? GFO might not be the best way to deal with them (if it does at all).

Joe Batt · May 12, 2018

This was the first test
https://www.triton-lab.de/en/showroom/aquarium/auswertung-b/icp-oes/57126/

I used Metasorb for 10 days and retested. No water changes or dosing, just feeding the fish after the cycle.

and this was the second
https://www.triton-lab.de/en/showroom/aquarium/auswertung-b/icp-oes/51627/

I still have a little copper,tin, zinc plus some aluminium.
I used DETOX for the copper and removed the block of Marine Pure (replaced it with NanoTech Bio spheres) to stop the Aluminium. I was hoping to remove the little aluminium in the tank with the Rowa as well a decreasing the PO4 (kind of a 2 for 1).
I suspect the tin is possibly from the PVC pipes that I built the manifold out of when I rebuilt the tank.

I am also half way through 6x15% water changes and will put Metasorp in again afterwards and retest.

I dont want to add corals until I have things tied down properly, so does it sound like a reasonable plan? Any further suggestions?

Randy Holmes-Farley · May 12, 2018

Definitely still some elevated, problematic metals in the second test. Do you know how they got there?

A rusting metal part is a good guess. Tin is a concern. Copper is borderline, IMO. Zinc is high. Those sound like corroding metal.

Joe Batt · May 12, 2018

That's the strange thing, no idea at all.
The tank had been stripped down and cleaned, new rocks and sand. I had checked and cleaned every pump and magnet in the tank, everything was in good condition. In fact the return pump was new, the skimmer was new and several pumps that had previous;y fed reactors had been removed when I built the manifold. That only leaves the two gyres and the chiller. The internal structure of the Hailea chiller, is an unknown, so that could be a possibility. I had also tested the RODI water and it was fine. My only thought was perhaps the rocks were leaching since I had bought them from another reeefer.

Randy Holmes-Farley · May 13, 2018

What type of sand?

Joe Batt · May 13, 2018

Can't remember the name, it wasn't RedSea but was from my local LFS so would have expected it to be OK. It wasn't live sand.

Randy Holmes-Farley · May 13, 2018

But it’s not black sand?

Joe Batt · May 13, 2018

Nope just common normal sand, nothing fancy.

There is no metal in it and I am always careful to keep screws etc out of the tank totally just in case.

The only other thing is an epoxy that I used for aqua-scaping, called M-Seal. Many of the reefers here use it with no problem and even a reputable LFS who builds tanks for people recommends it. The scape was built prior to the rocks being cycled for 4-6 weeks, in a big trash can in the garage. Any leaching, I would have expected to have passed prior to them going into the tank.

Randy Holmes-Farley · May 13, 2018

Joe Batt said:
Nope just common normal sand, nothing fancy.

There is no metal in it and I am always careful to keep screws etc out of the tank totally just in case.

The only other thing is an epoxy that I used for aqua-scaping, called M-Seal. Many of the reefers here use it with no problem and even a reputable LFS who builds tanks for people recommends it. The scape was built prior to the rocks being cycled for 4-6 weeks, in a big trash can in the garage. Any leaching, I would have expected to have passed prior to them going into the tank.

An epoxy that is not clearly filled with chunks of metal seems a very unlikely source.

Joe Batt · May 13, 2018

Will continue the water changes and Metasorp for another week and then try another test. After this, I'm at a bit of a loss if there is no improvement. Thanks for you help and thoughts Randy

Randy Holmes-Farley · May 13, 2018

You're welcome.

Good luck!

Hitman · Jul 3, 2018

What’s the difference if you have black or white sand @Randy Holmes-Farley ? I have a mix of black and white crushed coral for substrate and looking into getting rowaphos as high cap GFO just isn’t cutting it for my tank. I can’t seem to keep PO4 below 0.10 ppm to save my life.