1st time GFO user...questions

[Thumbster]

After three years I ordered some HC GFO from Kolar for my "keep it simple" 40 breeder due to my PO4 being .74 according to my Hanna checker.
I will be putting it in a 180 micron filter bag and it will be in my Tidal 110 HOB filter (450 GPH), the only filtration that I use for my tank, other than 30% monthly water changes.

The directions for the HC GFO say to use 1 tbs per 8 gallon. I know the bag in the HOB won't be as efficient as a reactor, but I was wondering if anyone has done something similar and what kind of PO4 reduction I should be expecting? I'm trying to avoid a sudden drop.
Thanks!

 

[EricR]

I'm running BRS HC GFO in 100 micron bag in Tidal 110 HOB on a 40 breeder with no sump.
I use 20 grams and have been seeing 0.06-0.08 ppm drop the first day when GFO is new.
By around day 4 or so, my PO4 has maybe gone down another couple hundredths ppm but then just stays pretty stable for a couple/few weeks.
I get about 1 month use out of HC GFO before I change it out.
*was using standard GFO before and, for me, the HC GFO basically just lasts longer

 

[Thumbster]

I'm running BRS HC GFO in 100 micron bag in Tidal 110 HOB on a 40 breeder with no sump.
I use 20 grams and have been seeing 0.06-0.08 ppm drop the first day when GFO is new.
By around day 4 or so, my PO4 has maybe gone down another couple hundredths ppm but then just stays pretty stable for a couple/few weeks.
I get about 1 month use out of HC GFO before I change it out.
*was using standard GFO before and, for me, the HC GFO basically just lasts longer

Awesome!
Sounds like we are doing exactly the same thing.
I have some more questions for you though.
Do you think 180 microns that I'll be using is too small?
Does the GFO turn into a rock, and do you have to take it out and break it up every now and then?
Would it take out more PO4 if you used more?
Thanks again!

 

[EricR]

Awesome!
Sounds like we are doing exactly the same thing.
I have some more questions for you though.
Do you think 180 microns that I'll be using is too small?
Does the GFO turn into a rock, and do you have to take it out and break it up every now and then?
Would it take out more PO4 if you used more?
Thanks again!

100-150 micron bags work good for me. 180 micron is slightly larger and GFO has some pretty fine particles but should be fine. *search some sites or wait for others to respond but I think 180 is probably good.

I don't have any issue with the GFO hardening, personally, but I think some/many do massage it and rinse periodically to keep it loose (if not using a reactor). *mine isn't packed tightly into the bag, more spread out in a thin layer and I do pull everything out of the HOB and rinse/inspect when I'm rinsing the Tidal sponge and changing out the layer of pond filter I use in it, about once per week.

Since I'm only using 20g, that's not a lot. It's more like 1 tablespoon instead of the 4 tbsp it would be if you went with the recommendation of 1 tbsp per 8 gallons. (I'm guessing water volume around 30 gallons for a 40 breeder with rock). I'm guessing using more would pull out more initially and last longer but I never tried more as I was worried about pulling out too much PO4 at once.
*I'd say start slow and see how it goes -- maybe half of what is recommended?

Final note -- I had to dose phosphate for a long time to maintain detectable levels, then it stayed stable on its own for a long time where I wanted it. At about the 4 year mark is when my PO4 finally started climbing.
-- I let it get up to 0.60 ppm before I decided to do something about it. (Mostly soft corals and they didn't seem to mind at all).
-- Currently, I wait until I see 0.20 ppm (testing weekly) then change the GFO.
-- Using only 20g, that usually gets me down into the 0.10-0.12 ppm range at the lowest and then I let it ride again until I see >0.20 (about 1 month).

EDIT -- you obviously need a way to keep the bag of GFO in place with good water flow passing through it.
Here's everything I have layered in my Tidal 110, from bottom to top:
1. Sponge that came with the HOB
2. Dual-layer pond filter pad cut from bulk roll
3. Bag of GFO and usually bag of ROX 0.8 carbon
4. Bag of Matrix that came with the HOB -- Original Seachem bag seemed too fine of mesh for my liking so I switched to using bag with coarser mesh, advertised as 2mm holes but really seem bigger, which is good.
-->bag of Matrix is what sits on top and holds the GFO bag in place while still letting flow through
***probably not the best way to run GFO but it's been working for me

 

[Randy Holmes-Farley Verified Community Expert]

There’s no way to easily judge the expected drop because it depends on how much exposed calcium carbonate surface you have, such as rock and sand, which will have phosphate bound to it (which will come off).

Just take it slow. :)

 

[Thumbster]

100-150 micron bags work good for me. 180 micron is slightly larger and GFO has some pretty fine particles but should be fine. *search some sites or wait for others to respond but I think 180 is probably good.

I don't have any issue with the GFO hardening, personally, but I think some/many do massage it and rinse periodically to keep it loose (if not using a reactor). *mine isn't packed tightly into the bag, more spread out in a thin layer and I do pull everything out of the HOB and rinse/inspect when I'm rinsing the Tidal sponge and changing out the layer of pond filter I use in it, about once per week.

Since I'm only using 20g, that's not a lot. It's more like 1 tablespoon instead of the 4 tbsp it would be if you went with the recommendation of 1 tbsp per 8 gallons. (I'm guessing water volume around 30 gallons for a 40 breeder with rock). I'm guessing using more would pull out more initially and last longer but I never tried more as I was worried about pulling out too much PO4 at once.
*I'd say start slow and see how it goes -- maybe half of what is recommended?

Final note -- I had to dose phosphate for a long time to maintain detectable levels, then it stayed stable on its own for a long time where I wanted it. At about the 4 year mark is when my PO4 finally started climbing.
-- I let it get up to 0.60 ppm before I decided to do something about it. (Mostly soft corals and they didn't seem to mind at all).
-- Currently, I wait until I see 0.20 ppm (testing weekly) then change the GFO.
-- Using only 20g, that usually gets me down into the 0.10-0.12 ppm range at the lowest and then I let it ride again until I see >0.20 (about 1 month).

EDIT -- you obviously need a way to keep the bag of GFO in place with good water flow passing through it.
Here's everything I have layered in my Tidal 110, from bottom to top:
1. Sponge that came with the HOB
2. Dual-layer pond filter pad cut from bulk roll
3. Bag of GFO and usually bag of ROX 0.8 carbon
4. Bag of Matrix that came with the HOB -- Original Seachem bag seemed too fine of mesh for my liking so I switched to using bag with coarser mesh, advertised as 2mm holes but really seem bigger, which is good.
-->bag of Matrix is what sits on top and holds the GFO bag in place while still letting flow through
***probably not the best way to run GFO but it's been working You’ve answered my questions and then some.

100-150 micron bags work good for me. 180 micron is slightly larger and GFO has some pretty fine particles but should be fine. *search some sites or wait for others to respond but I think 180 is probably good.

I don't have any issue with the GFO hardening, personally, but I think some/many do massage it and rinse periodically to keep it loose (if not using a reactor). *mine isn't packed tightly into the bag, more spread out in a thin layer and I do pull everything out of the HOB and rinse/inspect when I'm rinsing the Tidal sponge and changing out the layer of pond filter I use in it, about once per week.

Since I'm only using 20g, that's not a lot. It's more like 1 tablespoon instead of the 4 tbsp it would be if you went with the recommendation of 1 tbsp per 8 gallons. (I'm guessing water volume around 30 gallons for a 40 breeder with rock). I'm guessing using more would pull out more initially and last longer but I never tried more as I was worried about pulling out too much PO4 at once.
*I'd say start slow and see how it goes -- maybe half of what is recommended?

Final note -- I had to dose phosphate for a long time to maintain detectable levels, then it stayed stable on its own for a long time where I wanted it. At about the 4 year mark is when my PO4 finally started climbing.
-- I let it get up to 0.60 ppm before I decided to do something about it. (Mostly soft corals and they didn't seem to mind at all).
-- Currently, I wait until I see 0.20 ppm (testing weekly) then change the GFO.
-- Using only 20g, that usually gets me down into the 0.10-0.12 ppm range at the lowest and then I let it ride again until I see >0.20 (about 1 month).

EDIT -- you obviously need a way to keep the bag of GFO in place with good water flow passing through it.
Here's everything I have layered in my Tidal 110, from bottom to top:
1. Sponge that came with the HOB
2. Dual-layer pond filter pad cut from bulk roll
3. Bag of GFO and usually bag of ROX 0.8 carbon
4. Bag of Matrix that came with the HOB -- Original Seachem bag seemed too fine of mesh for my liking so I switched to using bag with coarser mesh, advertised as 2mm holes but really seem bigger, which is good.
-->bag of Matrix is what sits on top and holds the GFO bag in place while still letting flow through
***probably not the best way to run GFO but it's been working for me

You’ve answered all my questions and then some. Thank you very much for doing so!
I will do exactly as you’ve done and see what happens.
If I can drop it 1/10th a week or so until it gets to around .1 - .2, I will consider it a success.

Edit: not sure how I “quoted” you twice but I don’t know how to change it.

 

[Thumbster]

There’s no way to easily judge the expected drop because it depends on how much exposed calcium carbonate surface you have, such as rock and sand, which will have phosphate bound to it (which will come off).

Just take it slow. :)

It might get interesting. I’ve had most of this rock and sand either in an aquarium or a tote in the basement since the 90’s.

 

[landlubber]

Maybe just an anecdote but I had insane P04 readings as well and decided to run 2 bags of GFO hung in a high flow area of my sump and made the effort every couple of days to agitate the media so avoid channeling. The result was not as impactful as i'd hoped seeing less than 1ppm reduction a day.
I really disliked the gfo reactor I previously had but wanted a little more pace so reluctantly purchased a Nyos Torq and was shocked how much of a difference it made. Using half the media as I had in the bags when agitated properly was literally 10x more effective and with the effect being larger it was much easier to determine when the media was spent and needed replacement.

 

[EricR]

You’ve answered all my questions and then some. Thank you very much for doing so!
I will do exactly as you’ve done and see what happens.
If I can drop it 1/10th a week or so until it gets to around .1 - .2, I will consider it a success.

Edit: not sure how I “quoted” you twice but I don’t know how to change it.

Good luck and let us know how it works out.
It'll be interesting to see if your experience is similar to mine sense sounds like we're using pretty much the same setup yet there are so many variables it's hard to know what to expect.
*you'll probably be changing out for fresh GFO more often in the beginning until you get down to where you want to be. (For me, first day of fresh GFO had the most dramatic effect, then not much more after that but that was just in my one specific tank,,, so who knows?).

 

[Thumbster]

Well after 2 days, I'm still at .61 PO4
I tested .64 right before I put the 1.5 tbs of GFO (along with 4 tbs of Rox carbon) into the basket of the HOB filter. Yesterday I was at .61, and I got the same today. I think the original .74 measurement may have been an outlier.
So today I added 2 tbs of GFO to the original 1.5 bringing me closer to the "recommended" starting dose and I will see where I'm at tomorrow.
I also am going to lay the GFO bag horizontal vs standing up like I did have it. Maybe having the GFO spread out in the bag will expose more surface area instead of having it all balled up in the bottom of the bag. The carbon I will keep pretty tight in the bag to avoid it possibly breaking apart. I will cover both bags with the bag of rocks that came with the HOB. I do have the coarse sponge thing that came with the filter underneath all of this in the basket.
Also, the 180-micron bag seems to be working well for this particular brand and flavor of GFO. I had read that the non high capacity GFO has more fines so that's why I went with the HC stuff. Don't know if that is the case or not though.

 

[Randy Holmes-Farley Verified Community Expert]

Bag use is very slow, and release from rock and sand will make it a slow process.

 

[dwest]

Well after 2 days, I'm still at .61 PO4
I tested .64 right before I put the 1.5 tbs of GFO (along with 4 tbs of Rox carbon) into the basket of the HOB filter. Yesterday I was at .61, and I got the same today. I think the original .74 measurement may have been an outlier.
So today I added 2 tbs of GFO to the original 1.5 bringing me closer to the "recommended" starting dose and I will see where I'm at tomorrow.
I also am going to lay the GFO bag horizontal vs standing up like I did have it. Maybe having the GFO spread out in the bag will expose more surface area instead of having it all balled up in the bottom of the bag. The carbon I will keep pretty tight in the bag to avoid it possibly breaking apart. I will cover both bags with the bag of rocks that came with the HOB. I do have the coarse sponge thing that came with the filter underneath all of this in the basket.
Also, the 180-micron bag seems to be working well for this particular brand and flavor of GFO. I had read that the non high capacity GFO has more fines so that's why I went with the HC stuff. Don't know if that is the case or not though.

As mentioned earlier, go slow. I use 1/2 cup (8 tablespoons) in my 180 gallon mixed reef to roughly maintain phosphate levels. I replace mine every 3 weeks. Maintaining or slightly lowering vs getting down to a number is what I would do.

When I tried lowering to a low number, I ended up with dinos. It was without a doubt the worst year of my 30 something year reefing career.

 

[ChrisfromBrick]

After three years I ordered some HC GFO from Kolar for my "keep it simple" 40 breeder due to my PO4 being .74 according to my Hanna checker.
I will be putting it in a 180 micron filter bag and it will be in my Tidal 110 HOB filter (450 GPH), the only filtration that I use for my tank, other than 30% monthly water changes.

The directions for the HC GFO say to use 1 tbs per 8 gallon. I know the bag in the HOB won't be as efficient as a reactor, but I was wondering if anyone has done something similar and what kind of PO4 reduction I should be expecting? I'm trying to avoid a sudden drop.
Thanks!

if you’re going the gfo route, it might be better to get the brs reactor. That way you can tune the flow to let the top layer lightly dance.

Be careful with that stuff because it’s powerful.

 

[Thumbster]

Bag use is very slow, and release from rock and sand will make it a slow process.

Thanks! I am in no real hurry, the corals that I have (hammers, montiporas, stylo, toadstool, etc.) seem to be doing ok. I think I would actually prefer going slow.
These rocks have been soaking up who knows what, off and on, for a few decades and they may not be willing to give up their ghosts readily.

I blame myself for finally getting an ICP test done and then buying the Hanna PO4 tester.
If I'm still at .6 something a month from now, I might look into a mini reactor, as much as I want to keep things simple.

 

[Thumbster]

if you’re going the gfo route, it might be better to get the brs reactor. That way you can tune the flow to let the top layer lightly dance.

Be careful with that stuff because it’s powerful.

I have looked at them on the BRS site and might eventually get one if this road is a dead end.
I'm trying to keep things simple, I don't have a sump, nor a skimmer and there is not a whole lot of real estate on the back of this tank but, if necessary, I could find a way.

 

[Thumbster]

As mentioned earlier, go slow. I use 1/2 cup (8 tablespoons) in my 180 gallon mixed reef to roughly maintain phosphate levels. I replace mine every 3 weeks. Maintaining or slightly lowering vs getting down to a number is what I would do.

When I tried lowering to a low number, I ended up with dinos. It was without a doubt the worst year of my 30 something year reefing career.

I'm assuming that you have a reactor?
Ive been through the dinos which were replaced by GHA and now I've got a little bit of cyano.
Up to this point I have tried to manage things with water changes but decided to get an ICP done. When they sent me a trophy for the world's highest PO4 (I'm joking but it was 1.3 a couple months ago), I thought maybe I should start paying attention and I might actually have a decent looking tank.

 

[dwest]

I'm assuming that you have a reactor?
Ive been through the dinos which were replaced by GHA and now I've got a little bit of cyano.
Up to this point I have tried to manage things with water changes but decided to get an ICP done. When they sent me a trophy for the world's highest PO4 (I'm joking but it was 1.3 a couple months ago), I thought maybe I should start paying attention and I might actually have a decent looking tank.

I have a tunze skimmer that has a bag on the outlet. That’s where I place GFO. I put it in a bag first. So have have a bag in a bag

 

[dwest]

I'm assuming that you have a reactor?
Ive been through the dinos which were replaced by GHA and now I've got a little bit of cyano.
Up to this point I have tried to manage things with water changes but decided to get an ICP done. When they sent me a trophy for the world's highest PO4 (I'm joking but it was 1.3 a couple months ago), I thought maybe I should start paying attention and I might actually have a decent looking tank.

I disliked reactors. I felt they were too much work for me.

 

[EricR]

Like I tried to mention earlier, I have the bag of GFO laying horizontally across the top of the sponge that came with the Tidal 110 and that seems to give enough flow through the GFO to work well (for me).
*Bag of Matrix rock on top to hold everything in place

Without the sponge, the flow might not be as dispersed across the bag of GFO but I guess see how it goes.
*seems like there will be columns of water from the slits in the basket passing through only some parts of the GFO bag but not sure

 

[dwest]

Like I tried to mention earlier, I have the bag of GFO laying horizontally across the top of the sponge that came with the Tidal 110 and that seems to give enough flow through the GFO to work well (for me).
*Bag of Matrix rock on top to hold everything in place

Without the sponge, the flow might not be as dispersed across the bag of GFO but I guess see how it goes.
*seems like there will be columns of water from the slits in the basket passing through only some parts of the GFO bag but not sure

I bet your method is fine.