Dosing Questions and PO4 removal

[Ian Baxter]

Below are my test results since I started to add corals to my 120g. Fairly lightly stocked with mostly LPS and zoa's right now. The dates in Red are water change dates. Salifert for Ca and Mag. Hanna for PO4 and dKH.

I have BRS Pharma Mag Mix so I can raise the Mag. But I'm wondering if I should try two part dosing?

Also, to lower my PO4, should I use an algae scrubber or a GFO reactor?

Any advice will help.

3/29/20​

4/7/20​

4/12/20​

4/27/20​

5/3/20​

5/12/20​

5/19/20​

5/25/20​

5/31/20​

6/23/20​

7/3/20​

7/5/20​

7/20/20​

7/21/20​

7/22/20​

7/24/20​

7/25/20​

7/26/20​

Ca

350​

400​

420​

440​

450​

450​

450​

440​

450​

440​

415​

425​

425​

415​

420​

425​

dKH

7.3​

7.7​

8​

8.3​

8.3​

9.6​

8​

8.6​

7.3​

7.7​

6.9​

7​

6.9​

6.9​

6.7​

7.2​

Mg

960​

1020​

1110​

1110​

1170​

1140​

1140​

1140​

1170​

1170​

1170​

1185​

1170​

1200​

1200​

1185​

pH

8.2​

8​

8​

8​

8​

8​

8​

NO3

10​

10​

5​

5​

10​

10​

PO4

0.435​

0.454​

0.399​

Salinity

1.024​

1.025​

1.026​

1.026​

1.025​

1.026​

1.026​

1.026​

1.025​

1.027​

1.026​

1.026​

1.026​

1.026​

1.026​

1.026​

Temp

78.3​

78.3​

78.4​

78.8​

78.8​

78.8​

78.3​

78.4​

78.3​

78.1​

78.4​

78.6​

78.1​

78.4​

78.4​

78.1​

 

[neiltus]

GFO is what I use. Quicker, but you must monitor daily till you have experience or you will drive to zero quick. I run a half cup for a 70 gallon water volume. Monitor with a Hanna 736.

Also, bring Mg up and then get your dkh in line. Maybe buy a jug and pouch of soda ash as well as Ca.

 

[esther]

ROWAPhos does wonders for reducing PO4! I don’t use anything else.

 

[Randy Holmes-Farley Verified Community Expert]

Also, to lower my PO4, should I use an algae scrubber or a GFO reactor?

​

Both work fine, as do many other methods. There is no single "best" answer how to manage nutrients.

Below are my test results since I started to add corals to my 120g. Fairly lightly stocked with mostly LPS and zoa's right now. The dates in Red are water change dates. Salifert for Ca and Mag. Hanna for PO4 and dKH.

I have BRS Pharma Mag Mix so I can raise the Mag. But I'm wondering if I should try two part dosing?

8.4

78.4

78.1

You should not need much magnesium until you are dosing lots of alk and calcium.

A two part is certainly a fine way to go.

 

[Ian Baxter]

ROWAPhos does wonders for reducing PO4! I don’t use anything else.

Thank you. I will look into that.

 

[Ian Baxter]

Both work fine, as do many other methods. There is no single "best" answer how to manage nutrients.



You should not need much magnesium until you are dosing lots of alk and calcium.

A two part is certainly a fine way to go.

So if I start two part dosing, I should hold off on the Mag and see what happens?

 

[Ian Baxter]

GFO is what I use. Quicker, but you must monitor daily till you have experience or you will drive to zero quick. I run a half cup for a 70 gallon water volume. Monitor with a Hanna 736.

Also, bring Mg up and then get your dkh in line. Maybe buy a jug and pouch of soda ash as well as Ca.

I do have the Hanna 736, so that will help. When you monitor daily are you just testing? Trying to figure out a way to reduce PO4 that's not crazy difficult.

 

[neiltus]

I do have the Hanna 736, so that will help. When you monitor daily are you just testing? Trying to figure out a way to reduce PO4 that's not crazy difficult.

yes, I test daily when running gfo or rowa (both do the same thing but rowa works faster-you need to monitor if your not used to running this so you don't drive it to zero)....I also have and use a set of standards (under 10 bucks I think for the 736).

rowa states something like 1 g will remove 3ppm from 10 gallons. It does it pretty quick actually. so if your like 50ppb, plan and test accordingly.

Thinking about and watching what your doing is key.

 

[Randy Holmes-Farley Verified Community Expert]

So if I start two part dosing, I should hold off on the Mag and see what happens?

Commercial two parts incorporate it. If you DIY, use the magnesium as directed.

 

[Randy Holmes-Farley Verified Community Expert]

yes, I test daily when running gfo or rowa (both do the same thing but rowa works faster-you need to monitor if your not used to running this so you don't drive it to zero)....I also have and use a set of standards (under 10 bucks I think for the 736)

ROWAPhos is just a brand of gFO.
I don't think there is reason to think ROWAphos is different than other brands of GFO in speed of reduction.

 

[neiltus]

ROWAPhos is just a brand of gFO.
I don't think there is reason to think ROWAphos is different than other brands of GFO in speed of reduction.

I've noticed (not controlled) a quicker reduction with rowa vs just regular dusty gfo on more than one run. It could be a total subjective swag. I generally test twice a day when running and remove when I get around 10ppb. Rowa seems to get there quicker and be a little easier for me to drive to zero if I am not paying attention vs generic GFO.

I don't understand this observation.

I would assume all forms of GFO would hold the same PO4 at saturate +- a small amount.

 

[Randy Holmes-Farley Verified Community Expert]

I've noticed (not controlled) a quicker reduction with rowa vs just regular dusty gfo on more than one run. It could be a total subjective swag. I generally test twice a day when running and remove when I get around 10ppb. Rowa seems to get there quicker and be a little easier for me to drive to zero if I am not paying attention vs generic GFO.

I don't understand this observation.

I would assume all forms of GFO would hold the same PO4 at saturate +- a small amount.

They likely hold about the same per surface area. Surface area may vary.

I'm not sure what generic GFO means. I doubt any hobby companies are making GFO. They are all reselling commercial products they acquire.

 

[neiltus]

They likely hold about the same per surface area. Surface area may vary.

I'm not sure what generic GFO means. I doubt any hobby companies are making GFO. They are all reselling commercial products they acquire.

"generic" meaning GFO that looks like normal GFO without some coating or stabilizer. e.g. BRS bulk GFO.

I've only used about 5 or 6 different labeled GFO products, many look like what we consider normal, others have a coating or something added. I doubt this addition does anything on the total volume absorbed by any product.

It could be bias, (not saying one is better than the other), but I normally test via 736 at 12h when I run gfo. A normal charge of 30g BRS gfo when I do run it usually gets me to my pull the product stage in about a week to 10 days (15ppb). I tend to get there a lot quicker with the same charge of Rowa-like closer to 72 hours.