GFO: Silica vs PO4 experiment

[Miami Reef]

I’m thinking of dosing a beaker with 1ppm silica and 0.05ppm PO4, then running some GFO to see how much silica and phosphates it removes.

These are the questions I would like to answer:

Will GFO remove phosphates to undetectable if there is sufficient silica present?

Will GFO switch over to predominantly removing silica when phosphates reach a certain low point?


Backstory: I like my PO4 in my aquarium very low to almost undetectable, but I like to dose silica for sponges and diatoms. A part of me thinks that the GFO will stop adsorbing phosphates and switch to silica when PO4 gets too low.

I need to use GFO to maintain my phosphate levels.


Can someone help me design controls and tell me what I would need to ensure this experiment answers my questions?



I have a Hanna PPB PO4 checker, Hanna silica LR checker, sodium silicate, sodium phosphate, a GFO reactor, BRS high capacity GFO, beakers of various sizes, and instant ocean salt.

In my aquarium:

I like to maintain my phosphates from 0.01-0.03ppm

I would prefer to maintain my silica from 0.50ppm-1ppm

 

[Miami Reef]

I’m starting it:

Took about 2.5L of tank water.

Filtered all water test samples with a 0.45um syringe.

Starting PO4: 17ppb
Starting Si: 0.79ppm

Rinsed 1tsp of GFO in a media bag and added it to the beaker with the magnetic stirrer.

 

[Rick Mathew]

I’m thinking of dosing a beaker with 1ppm silica and 0.05ppm PO4, then running some GFO to see how much silica and phosphates it removes.

These are the questions I would like to answer:

Will GFO remove phosphates to undetectable if there is sufficient silica present?

Will GFO switch over to predominantly removing silica when phosphates reach a certain low point?


Backstory: I like my PO4 in my aquarium very low to almost undetectable, but I like to dose silica for sponges and diatoms. A part of me thinks that the GFO will stop adsorbing phosphates and switch to silica when PO4 gets too low.

I need to use GFO to maintain my phosphate levels.


Can someone help me design controls and tell me what I would need to ensure this experiment answers my questions?



I have a Hanna PPB PO4 checker, Hanna silica LR checker, sodium silicate, sodium phosphate, a GFO reactor, BRS high capacity GFO, beakers of various sizes, and instant ocean salt.

In my aquarium:

I like to maintain my phosphates from 0.01-0.03ppm

I would prefer to maintain my silica from 0.50ppm-1ppm

One thing that occurred to me is that the PO4 measurement is time sensitive…meaning that it will decrease over time without any GFO or any other Phosphorous absorber. We have seen this multiple times in many different experiments. In tank water that is “bio-active” it is consumed. So you might want to set up your experiment with a fresh preparation of salt water to minimize this effect and to compare the results to your tank water results …this could give you a way to partially differentiate the “storage effect” from the adsorption of the PO4 via the GFO…Just a thought

 

[Miami Reef]

From the above experiment:

Starting PO4: 17ppb
Starting Si: 0.79ppm

After 1 tsp GFO overnight:

PO4: 2ppb
Si: 0.21ppm


IMO: I used too much GFO. I wanted to experiment what happens if there is sufficient Si and PO4, but not enough GFO: Will phosphates become displaced by Silica on the GFO if there is much more Si compared to PO4?

One thing that occurred to me is that the PO4 measurement is time sensitive…meaning that it will decrease over time without any GFO or any other Phosphorous absorber. We have seen this multiple times in many different experiments. In tank water that is “bio-active” it is consumed. So you might want to set up your experiment with a fresh preparation of salt water to minimize this effect and to compare the results to your tank water results …this could give you a way to partially differentiate the “storage effect” from the adsorption of the PO4 via the GFO…Just a thought

Thank you. For the next experiment, I will use brand new ASW.

I don’t have work today because of Christmas, so it’s the perfect time to test this out. :)

 

[Miami Reef]

Take 2:

New saltwater made with instant ocean purple.

Dosed PO4 and silica:

PO4: 30ppb
Si: >2ppm (it flashed) (I tried dosing half a drop).

I rinsed half a tsp of GFO in beakers of RO/DI.

I then added the GFO directly to the beaker. I didn’t use a media bag because I wanted the GFO to very gently tumble.

 

[MnFish1]

Take 2:

New saltwater made with instant ocean purple.

Dosed PO4 and silica:

PO4: 30ppb
Si: >2ppm (it flashed) (I tried dosing half a drop).

I rinsed half a tsp of GFO in beakers of RO/DI.

I then added the GFO directly to the beaker. I didn’t use a media bag because I wanted the GFO to very gently tumble.

I would suggest that you have a couple controls - PO4 alone and Si alone. And with and without GFO - to take care of the issue mentioned by Rick Mathew. Merry Christmas

 

[Miami Reef]

Results are in from the previous experiment:

Starting PO4: 30ppb
Starting Si: >2ppm (flashing)

Added 1/2tsp of GFO


After several hours:

PO4: 15ppb
Si: >2.00ppm (still flashing)

I conclude that GFO primarily targets phosphates over silica. :)

I hypothesized that GFO would prefer silica if it was higher than 2.00ppm (compared to <0.10ppm PO4). I’m glad to have been wrong. :)


I don’t really believe I needed a control for this experiment. I’m happy with these results for my personal use.

I would like to know the changes in PO4 and silica after continuing this same experiment over the next day. I think the phosphates will continue to decrease.

 

[MnFish1]

Results are in from the previous experiment:

Starting PO4: 30ppb
Starting Si: >2ppm (flashing)

Added 1/2tsp of GFO


After several hours:

PO4: 15ppb
Si: >2.00ppm (still flashing)

I conclude that GFO primarily targets phosphates over silica. :)

I hypothesized that GFO would prefer silica if it was higher than 2.00ppm (compared to <0.10ppm PO4). I’m glad to have been wrong. :)


I don’t really believe I needed a control for this experiment. I’m happy with these results for my personal use.

I would like to know the changes in PO4 and silica after continuing this same experiment over the next day. I think the phosphates will continue to decrease.

True - but you're publishing them for an entire community. There is no way to know, based on your results, what's happening. adding above the amount of silicon testable (I assume thats what you mean by 'flashing' - means the silicon could have dropped far more than the PO4 - but who knows.

 

[Miami Reef]

True - but you're publishing them for an entire community. There is no way to know, based on your results, what's happening. adding above the amount of silicon testable (I assume thats what you mean by 'flashing' - means the silicon could have dropped far more than the PO4 - but who knows.

You are correct. I definitely should have dosed less than above 2ppm. That was a mistake on my part.

The Si still showed a dark blue color, so there was still significant Si present, but the PO4 still dropped by 50%.

I just wanted to see if phosphates would still adsorb on the GFO even if elevated Si was present.


The main thing to track in this experiment IMO was the PO4. That was the main goal. Silica wasn’t substantially adsorbed (Or else it would have been less than 2ppm).

It was a rough experiment. I really want to see if phosphates can drop to undetectable even with >2.00ppm Si present.

 

[Miami Reef]

After the next day results:

Initial PO4: 30ppb
Initial Si: >2.00ppm

Added 1/2 tsp GFO to 2L beaker

Later that day:

PO4: 15ppb
Si: >2.00ppm

The next day (today):

PO4: 4ppb
Si: 1.66ppm

 

[Dan_P]

One thing that occurred to me is that the PO4 measurement is time sensitive…meaning that it will decrease over time without any GFO or any other Phosphorous absorber. We have seen this multiple times in many different experiments. In tank water that is “bio-active” it is consumed. So you might want to set up your experiment with a fresh preparation of salt water to minimize this effect and to compare the results to your tank water results …this could give you a way to partially differentiate the “storage effect” from the adsorption of the PO4 via the GFO…Just a thought

Was the sample filtered through a syringe filter in the experiments you refer to? I know bleach was used in one series of experiments.

 

[Rick Mathew]

Was the sample filtered through a syringe filter in the experiments you refer to? I know bleach was used in one series of experiments.

No the control samples were given no special treatment ..the samples were taken from the tank place in a container and tested at various intervals

 

[Dan_P]

I’m thinking of dosing a beaker with 1ppm silica and 0.05ppm PO4, then running some GFO to see how much silica and phosphates it removes.

These are the questions I would like to answer:

Will GFO remove phosphates to undetectable if there is sufficient silica present?

Will GFO switch over to predominantly removing silica when phosphates reach a certain low point?


Backstory: I like my PO4 in my aquarium very low to almost undetectable, but I like to dose silica for sponges and diatoms. A part of me thinks that the GFO will stop adsorbing phosphates and switch to silica when PO4 gets too low.

I need to use GFO to maintain my phosphate levels.


Can someone help me design controls and tell me what I would need to ensure this experiment answers my questions?



I have a Hanna PPB PO4 checker, Hanna silica LR checker, sodium silicate, sodium phosphate, a GFO reactor, BRS high capacity GFO, beakers of various sizes, and instant ocean salt.

In my aquarium:

I like to maintain my phosphates from 0.01-0.03ppm

I would prefer to maintain my silica from 0.50ppm-1ppm

I just read this today. Sorry about being late to the party.

GFO adsorption of silicate and phosphate would be simultaneous, i.e., ”no switching”. The chemical species that binds the strongest might even displace the other from the GFO, e.g., maybe PO4 would kick out SiO4. To test this I would saturate a sample of GFO with silicate, rinse it and then measure how much PO4 it binds compared to new GFO. For a complete study, saturate GFO with PO4 and then see if it binds silicate as well as new GFO.