Nailing phosphate to a stable level with GFO?

[WillpoleReefers]

I have set up a new system, water volume approx 1100L and it is intended to be SPS dominated in the long term. The tank has been running about 4 months, with the sump cycled a few months earlier than that, that has a compartment with deep gravel and rock. I ended up leading with fish and we are pretty well up to the planned maximum. Some are greedy, ended up with a fair sized greedy gem tang amongst others, fair input and output of phosphate all considered. The tank is keeping a few hammers and torch corals fine, plus a small Acropora frag, it’s still very understocked with corals. I appreciate there are many and varied opinions on target phosphate levels but I have chosen to keep the level at less than 0.1 ppm given the planned SPS stocking. Want to drive it rather than just accept what’s thrown at me. Unsurprisingly given the fish bioload phosphate started to rise and hit 0.25 ppm (Hanna ULR checker used below 0.2ppm , Salifert kit when it went too high). Decided to start to learn how to use GFO and set up 500g in a reactor. It worked beautifully , phosphate going down a bit faster than perhaps ideal the first 2 days, 0.1 ppm the first day, after 8 days the drop has slowed and we have hit what may be a stable level of 0.073 ppm, ideal.

Question is how do I nail this here? Is that easy using GFO or am I likely to seesaw as a result of refreshing the GFO? Maybe I should reduce the quantity to 250g when I reload the reactor? I was planning to do that when I saw phosphate starting to rise a little. Don’t want to crash the level, and am aiming for stability. Can I even achieve this with permanent use of GFO or is it more of a blunderbuss tool ? Advice from those experienced using GFO appreciated!

Steve

 

[Timfish]

You'll need to keep checking it. Just about everything in your tank is messing with phosphorus. Sponges and biofilms are sequestering it. Biofilms are also messing with the sorbtion properties of the rock and sand. Depending on what and how much your corals are being fed tehy might actually be a source as they feed on particulate and organic P and release inorganic P.

Fig 4 from "Phosphorus metabolism of reef organisms with algal symbionts"

https://esajournals.onlinelibrary.wiley.com/doi/abs/10.1002/ecm.1217?casa_token=ziDzrEEJ8g0AAAAA%3AHnfuGTIntMdqOtx2ij-lnoTh7qVg8VBhYFz98e60zfBEvx5IcIVGhmlpUYmzIJuqUNVm0sG8_0vth6lq

 

[WillpoleReefers]

You'll need to keep checking it. Just about everything in your tank is messing with phosphorus. Sponges and biofilms are sequestering it. Biofilms are also messing with the sorbtion properties of the rock and sand. Depending on what and how much your corals are being fed tehy might actually be a source as they feed on particulate and organic P and release inorganic P.

Fig 4 from "Phosphorus metabolism of reef organisms with algal symbionts"

https://esajournals.onlinelibrary.wiley.com/doi/abs/10.1002/ecm.1217?casa_token=ziDzrEEJ8g0AAAAA%3AHnfuGTIntMdqOtx2ij-lnoTh7qVg8VBhYFz98e60zfBEvx5IcIVGhmlpUYmzIJuqUNVm0sG8_0vth6lq

Thanks for the info will read. I was expecting a fairly dynamic ride in a new tank. Coral population growing. 80 percent Marco rock 20 percent real. All will influence things as the tank matures. I would just like to be able to drive the phosphate level in the face of all this!

 

[Pod_01]

Just a comment, GFO can remove trace elements as well.

From my experience I killed lot more corals messing with phosphates vs. other aspects of reefing. Especially SPS didn’t like it when I was real good at nailing PO4 levels.

Results these days with lot less nails and hammers:

Good luck, and maybe consider using very few nails…

 

[WillpoleReefers]

Just a comment, GFO can remove trace elements as well.

From my experience I killed lot more corals messing with phosphates vs. other aspects of reefing. Especially SPS didn’t like it when I was real good at nailing PO4 levels.

Results these days with lot less nails and hammers:

Good luck, and maybe consider using very few nails…

Ok that’s interesting input. Thanks for sharing. Prob best not to overdo phosphate control. I was thinking of a refugium at some point that might help the issue more naturally. Wonder what trace elements it sucks out, and whether it is important ones. Not iron I assume

 

[Randy Holmes-Farley]

I think that there are many sinks for certain trace elements, and I would not change husbandry practices because any one is a concern. In fact, all nutrient export methods likely consume trace elements.

 

[WillpoleReefers]

At some point will do an ICP-MS on this tank. Be interesting to see. Yes I guess even a refugium growing stuff isn’t a free lunch.

 

[Stang67]

Refugium and skimmer. Gfo only in a situation that warrents it.

 

[East1]

i would recommend biopellets particularly the brown ones from DVH imports - they are a carbon pellet with GFO so phosphate binds to the pellet and is then processed by creating a higher local phosphate gradient for bacteria.

these will reduce your P level like GFO but in a biological way and so won’t cause the spikes associated with GFO use.

you can then tailor adding phosphate directly as a dosing solution or managing via your feeding to keep a stable level.

in my experience corals especially acropora will stress heavily if the P level swings too much, so stability is an order of magnitude more important than the absolute value.

 

[WillpoleReefers]

Yes it’s swings I worry about. Reading that reference on P it’s obvious the zooxanthellae need to be in a stable population situation adapted to the particular nutrient level. Rather like the nitrate story

 

[Randy Holmes-Farley]

i would recommend biopellets particularly the brown ones from DVH imports - they are a carbon pellet with GFO so phosphate binds to the pellet and is then processed by creating a higher local phosphate gradient for bacteria.

these will reduce your P level like GFO but in a biological way and so won’t cause the spikes associated with GFO use.

you can then tailor adding phosphate directly as a dosing solution or managing via your feeding to keep a stable level.

in my experience corals especially acropora will stress heavily if the P level swings too much, so stability is an order of magnitude more important than the absolute value.

That is not a correct interpretation on the part of whoever made the original claim. GFO does not raise the local concentration of phosphate unless it has excess phosphate on it and is actively desorbing phosphate to the bulk water.

Treat it as a marketing gimmick lacking science.

 

[bobnicaragua]

I have 2 bags with a mix of carbon and GFO in my sump. I change one of the bags every 2 weeks. My system tends to hang around .15 phosphates.

Running GFO passively, not in a reactor, is safer, but less efficient. There’s nothing wrong with using GFO, just go slow.

 

[East1]

That is not a correct interpretation on the part of whoever made the original claim. GFO does not raise the local concentration of phosphate unless it has excess phosphate on it and is actively desorbing phosphate to the bulk water.

Treat it as a marketing gimmick lacking science.

I wasn't talking about GFO by itself, but NP Biopellets by DVH Imports. It's a carbon polymer pellet mixed with GFO, so that the phosphate binds to the biopellet and locally (within the context of the 5mm pearl) the phosphate bound at the surface to GFO within the carbon matrix gives bacteria a site where they can process it without competition from anything else in the reef. As the carbon gets used the pellet breaks down exposing fresh sites for P to bind to.

That makes this kind of biopellet more effective at removing P than conventional beige biopellets

 

[Randy Holmes-Farley]

I wasn't talking about GFO by itself, but NP Biopellets by DVH Imports. It's a carbon polymer pellet mixed with GFO, so that the phosphate binds to the biopellet and locally (within the context of the 5mm pearl) the phosphate bound at the surface to GFO within the carbon matrix gives bacteria a site where they can process it without competition from anything else in the reef. As the carbon gets used the pellet breaks down exposing fresh sites for P to bind to.

That makes this kind of biopellet more effective at removing P than conventional beige biopellets

I understand what you are saying, and it is not correct. Zeovit makes (or made) the same false claim about ammonia on their zeolite.

Bacteria cannot use an ion bound to a polymer. It must come off first for the bacteria to take it up, and hence the bioavailability is determined by the dissolved ion concentration near the bacteria surface.

A binder always reduces the local bioavailability by lowering the local concentration of the element being bound, except when it is loaded with so much that it is actively releasing phosphate to the water.

 

[East1]

I understand what you are saying, and it is not correct. Zeovit makes (or made) the same false claim about ammonia on their zeolite.

Bacteria cannot use an ion bound to a polymer. It must come off first for the bacteria to take it up, and hence the bioavailability is determined by the dissolved ion concentration near the bacteria surface.

A binder always reduces the local bioavailability by lowering the local concentration of the element being bound, except when it is loaded with so much that it is actively releasing phosphate to the water.

what conditions would be needed to break the bond from the PO4 to the GFO to make it available to bacteria?

 

[Formulator]

I understand what you are saying, and it is not correct. Zeovit makes (or made) the same false claim about ammonia on their zeolite.

Bacteria cannot use an ion bound to a polymer. It must come off first for the bacteria to take it up, and hence the bioavailability is determined by the dissolved ion concentration near the bacteria surface.

A binder always reduces the local bioavailability by lowering the local concentration of the element being bound, except when it is loaded with so much that it is actively releasing phosphate to the water.

Are we sure about this? There are several mechanisms for phosphate uptake by bacteria, including high affinity active transport facilitated by membrane proteins and ATP, not just diffusion. There are also phosphate solubilizing bacteria which secrete organic acids to solubilize inorganic rock phosphorus and metal bound phosphate. These are primarily found in soil and marine sediments, but theoretically having a polymer substrate for the bacteria to colonize that is full of bound up phosphate could facilitate this type of phosphate metabolism.

Maybe this just doesn’t happen in our tanks, but spitballing here. Are the hobby manufacturers really putting that much effort into making snake oil?

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7866108/

 

[Randy Holmes-Farley]

what conditions would be needed to break the bond from the PO4 to the GFO to make it available to bacteria?

Lowering the phosphate concentration in the water will cause net desorption. It is always coming on and off in equilibrium with how much is in the water.

 

[Randy Holmes-Farley]

Are we sure about this? There are several mechanisms for phosphate uptake by bacteria, including high affinity active transport facilitated by membrane proteins and ATP, not just diffusion. There are also phosphate solubilizing bacteria which secrete organic acids to solubilize inorganic rock phosphorus and metal bound phosphate. These are primarily found in soil and marine sediments, but theoretically having a polymer substrate for the bacteria to colonize that is full of bound up phosphate could facilitate this type of phosphate metabolism.

Maybe this just doesn’t happen in our tanks, but spitballing here. Are the hobby manufacturers really putting that much effort into making snake oil?

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7866108/

All of those can and likely do happen in reef tanks, None of them make it plausible that a mineral capable of binding phosphate is making it more bioavailable to an overlying layer of bacteria.

Certainly the nature of the transport is unimportant because an ion must be in solution to be used by either active or passive uptake.

As to the desorbing phosphate from GFO (or ammonia from a zeolite) with acid, that certainly can happen, but it’s a one time thing. It is not the case that bacteria are moving across these surfaces like lawnmowers desorbing phosphate and sucking it up.

 

[Formulator]

All of those can and likely do happen in reef tanks, None of them make it plausible that a mineral capable of binding phosphate is making it more bioavailable to an overlying layer of bacteria.

Certainly the nature of the transport is unimportant because an ion must be in solution to be used by either active or passive uptake.

As to the desorbing phosphate from GFO (or ammonia from a zeolite) with acid, that certainly can happen, but it’s a one time thing. It is not the case that bacteria are moving across these surfaces like lawnmowers desorbing phosphate and sucking it up.

Fair point regarding the nature of uptake. A lot of what I do these days involves weak interactions between molecules, such as hydrophobic adsorption and colloidal van der waals forces. I sometimes forget the importance of charge mediated exchange in driving trans-membrane processes even though that is the predominant mechanism.

Just for fun, probing this further, what about adherent bacteria that could potentially be co-localized on the phosphate rich media? I get the lawnmower point, but if you had a high surface area media that was attractive to adherent phosphate solubilizing bacteria, and had high affinity for binding phosphate, could this work to regulate phosphate in the system? Not asking if this type of media or bacterial culture exists, but theoretically would it be something worth exploring?

 

[Randy Holmes-Farley]

if the area between the bacterium and the GFO is acidic to release phosphate, then more phosphate will not bind. The kinetics of getting the phosphate from the water then under the bacterium to the GFO is also problematic.