GFO basically useless in very high phosphate environment?

[BigJohnny]

@Randy Holmes-Farley

Let me start off by saying I am personally not a fan of GFO, and I rarely ever use it. Even in small amounts I have had issues where it worked too quickly and stressed corals.

Now having said that, my phosphates have spiked up from .18 to .6 ppm due to a fish dying in the rockwork without me knowing, so I have chosen to use it to help me bring the levels down. I dont normally test for phosphate because it stays .1 - .2 ppm which is my preferred range, and that's where I'm trying to get it back to slowly.

I have 110g water volume and I used 7 tablespoons BRS GFO (standard, not high capacity), which is about 1/4th the recommended amount. It appears to have exhausted in about 3 days max with minimal impact. (Color change test kit so cant really tell, but my hanna is not reliable)

Is there anyway to determine how quickly its being exhausted? I'm using a bag so cant test reactor effluent, just wondering if you can calculate by weight and estimate etc.

I don't want to increase the amount I am using at once unless necessary, but if I cant test a large enough difference to see when its exhausted I'm afraid I'll miss the window and it will release back into the water before i replace it. Is that even really a concern or would the water have to be much lower in phosphate for that to occur?

Thoughts?

Thanks

 

[Reeferdood]

Hey Johnny,
GFO works best if in a reactor. IMHO, the reason you aren't pulling the phosphate down is because you have it in a bag.
Is it possible for you to fluidize the media? It can pull phosphate down quickly but unless you want a algae infestation I would get a reactor for the GFO.
Once the levels are where you want them then you can try another form of export if you don't like GFO.

 

[Jason mack]

I’ve had problems burning through rowaphos ... I found by adding a diy algea turf scrubber I am able too reduce the time it takes too deplete ...

 

[Jason mack]

@Randy Holmes-Farley

Let me start off by saying I am personally not a fan of GFO, and I rarely ever use it. Even in small amounts I have had issues where it worked too quickly and stressed corals.

Now having said that, my phosphates have spiked up from .18 to .6 ppm due to a fish dying in the rockwork without me knowing, so I have chosen to use it to help me bring the levels down. I dont normally test for phosphate because it stays .1 - .2 ppm which is my preferred range, and that's where I'm trying to get it back to slowly.

I have 110g water volume and I used 7 tablespoons BRS GFO (standard, not high capacity), which is about 1/4th the recommended amount. It appears to have exhausted in about 3 days max with minimal impact. (Color change test kit so cant really tell, but my hanna is not reliable)

Is there anyway to determine how quickly its being exhausted? I'm using a bag so cant test reactor effluent, just wondering if you can calculate by weight and estimate etc.

I don't want to increase the amount I am using at once unless necessary, but if I cant test a large enough difference to see when its exhausted I'm afraid I'll miss the window and it will release back into the water before i replace it. Is that even really a concern or would the water have to be much lower in phosphate for that to occur?

Thoughts?

Thanks

Gfo won’t release it back into the water .. but only when it’s changed will it be removed and you will see the difference when you test again

 

[Gareth elliott]

If going to use a bag phosgaurd or other aluminum based removal media will be more effective than GFO.

 

[BigJohnny]

Hey Johnny,
GFO works best if in a reactor. IMHO, the reason you aren't pulling the phosphate down is because you have it in a bag.
Is it possible for you to fluidize the media? It can pull phosphate down quickly but unless you want a algae infestation I would get a reactor for the GFO.
Once the levels are where you want them then you can try another form of export if you don't like GFO.

Thanks for posting but I am intentionally running it in a bag because it's less aggressive than a reactor. I do not want to pull it down quickly. I've been reefing for almost 10 years so I've tried it in a reactor before.

 

[BigJohnny]

I’ve had problems burning through rowaphos ... I found by adding a diy algea turf scrubber I am able too reduce the time it takes too deplete ...

I have a fuge, i 'm using the gfo as a secondary tool only for this isolated event.

 

[BigJohnny]

Gfo won’t release it back into the water .. but only when it’s changed will it be removed and you will see the difference when you test again

That's actually not true, GFO will release phosphate back into the water if its "exhausted" and the surrounding water is lower in phosphate. That is a fact, I am just not sure how big the difference needs to be for that to happen.

 

[BigJohnny]

If going to use a bag phosgaurd or other aluminum based removal media will be more effective than GFO.

I think thats only true if the GFO clumps, which is one of the main reasons it should be fluidized. Mine is hanging in a bag right in front of my skimmer output and will not clump up that way.

 

[Reeferdood]

Thanks for posting but I am intentionally running it in a bag because it's less aggressive than a reactor. I do not want to pull it down quickly. I've been reefing for almost 10 years so I've tried it in a reactor before.

You can try LC at a lower dose if GFO isn't working for you...
I've been reefing for 15+ years and still learn something new every day..

 

[Reefahholic]

If you have an elevated level of 1.0 -3.0 then you will deplete the GFO like crazy and burn through a lot of money. There are other ways to deal with it.

 

[BigJohnny]

You can try LC at a lower dose if GFO isn't working for you...
I've been reefing for 15+ years and still learn something new every day..

Yea I've definitely considered LC, the precip scares me though so trying small amounts of gfo first. No doubt I am always learning I just wanted you to know I'm not a new reefer and am aware that it can work more efficiently in a reactor. I mainly created this thread to see if randy knew a way to estimate how fast a given amount of gfo would exhaust in a set amount of water at .5ppm.

I know I could just use more or a reactor but I really dont want to reduce it any faster. I'm just concerned it will be basically useless the way I'm using it now without being able to tell when its exhausted and obviously very expensive if I just preemptively replace it every 2 or 3 days when it's removing small amounts.

 

[BigJohnny]

If you have an elevated level of 1.0 -3.0 then you will deplete the GFO like crazy and burn through a lot of money. There are other ways to deal with it.

It's at .5 ppm not >1 ppm, but still, even at that concentration I'm pretty sure its exhausting in a few days. My problem is my test kit wont confirm changes of less than .1 ppm in this high range and thats about as fast as I want to bring it down per week. So I'm trying to see if there's a way to estimate exhaustion relatively accurately.

If I double the amount of gfo I'm concerned I'll have issues because I've stressed corals with that same amount in a bag before. It also may exhaust equally as fast just pull it down quicker so no benefit to me.

LC or large water changes (I dont want to do water changes for several reasons) seem like better options, but I'm just trying this more subtle approach first. Besides slowed growth and a hit to coloration on some acros I'm seeing no ill effects, so no rush at this point.

 

[Dan_P]

You can estimate the rate of use if you know the GFO’s capacity, i.e., mg of PO4 adsorbed per kg of GFO, the number of gallons in your system and the current concentration of PO4 in the system.

The math is...

ppm of PO4 in the system times the gallons of the system times 3.7 liters per gallon.

This gives the total mg of PO4 you have. Divide the GFO capacity by the total amount of PO4 to get the kg of GFO needed. Since it is likely that PO4 is adsorbed to the aragonite in your system, you will not likely drive down the PO4 to zero with this quantity. Also, with GFO in a bag, the removal rate of PO4 will be slow compared to GFO in a reactor.

 

[Javamahn]

LC or large water changes (I dont want to do water changes for several reasons) seem like better options, but I'm just trying this more subtle approach first. Besides slowed growth and a hit to coloration on some acros I'm seeing no ill effects, so no rush at this point.

Can I ask why no large water change? Seems the least detrimental and most controlable

 

[BigJohnny]

You can estimate the rate of use if you know the GFO’s capacity, i.e., mg of PO4 adsorbed per kg of GFO, the number of gallons in your system and the current concentration of PO4 in the system.

The math is...

ppm of PO4 in the system times the gallons of the system times 3.7 liters per gallon.

This gives the total mg of PO4 you have. Divide the GFO capacity by the total amount of PO4 to get the kg of GFO needed. Since it is likely that PO4 is adsorbed to the aragonite in your system, you will not likely drive down the PO4 to zero with this quantity. Also, with GFO in a bag, the removal rate of PO4 will be slow compared to GFO in a reactor.

Thanks, yea that's what I getting at with Randy. My problem is I cant find the GFOs capacity anywhere and I figured he would know it. I believe he's done some experiments with it as well.

To your other points I am not even remotely interested in driving my po4 to zero, just restore it to it's normal range of .1 to .2 ppm. Again, I am intentionally using it in a bag over a reactor because its slower. I dont want it to happen quickly.

 

[BigJohnny]

Can I ask why no large water change? Seems the least detrimental and most controlable

As I said previously the precipitation scares me. I know there are ways to reduce the chance any gets into your system but the risk is there none the less. If the gfo doesnt work out after a few iterations I will definitely use some LC. I have some in my garage.

I just replaced the 7 tbsp with a fresh 10 tbsp so well see if there is any change over the next 48 hrs.

 

[Dan_P]

Thanks, yea that's what I getting at with Randy. My problem is I cant find the GFOs capacity anywhere and I figured he would know it. I believe he's done some experiments with it as well.

To your other points I am not even remotely interested in driving my po4 to zero, just restore it to it's normal range of .1 to .2 ppm. Again, I am intentionally using it in a bag over a reactor because its slower. I dont want it to happen quickly.

What GFO are you using?

 

[Dan_P]

https://www.researchgate.net/public...val_Demonstration_preparation_and_field_study

I only had access to the abstract and figures for the article above, but from what little I could readof it, I would use 50 mg PO4 per gram of GFO as a high estimate of its capacity. How it is made and stored and how old it is effects the capacity. Using this generous capacity will prevent removing PO4 too quickly from your system.

 

[BigJohnny]

What GFO are you using?

I'm using brs bulk gfo, regular not high capacity.