Nitrate removal w/standard live rock

[5pacey]

I have not seen this discussed yet so I thought I'll bring it up. This occurred to me while reading the description of how Seachem's de*nitrate works. I do not use it but the product drew my interest, and it basically is very similar to small size live rock rubble.

Basically, we know that live rock is porous and it is the pores which provide surface are for nitrifying bacteria to live and to conduct their business of turning ammonia into nitrate via nitrite. This happens in the aerobic conditions, or IOW where oxygen is available. We also know that it is the anaerobic conditions which support the existence of bacteria which turn Nitrate into Nitrogen. There are various strains of those, some like sulphur, some like carbon to eat etc. But all of them require anaerobic conditions.

Seachem says that for de*nitrate to work you have to maintain very low flow, 50GPH or less, in order for the bacteria in the top layers of the pores to convert ammonia into nitrate with sufficient intensity as to consume all available oxygen, thus depriving the deeper dwelling bacteria of it and creating the anaerobic conditions conducive to the bacteria which convert Nitrate to Nitrogen. Thus causing the de-nitrification process.

So... given that de*nitrate essentially simulates a form of live rock... wouldn't the same principle apply to live rock as well? IOW, if we reduced the flow past a section w/live rock to say 50Gph or less, wouldn't it start functioning as a de-nitrifying filter the same way as de*nitrate is suppose to?

Spacey

 

[5pacey]

Bump, anyone?

Spacey

 

[SantaMonica]

Doesn't matter what the flow on the outside of a rock is; the denitrifying part is on the inside, and by definition is cut-off from flow (otherwise, flow would bring oxygen in).

 

[5pacey]

No quite... water that gets in through the pores is oxygenated. Unless bacteria living closer to the surface strip it of oxygen it will still be oxygenated when it gets deeper into the pores. In order for the close to the surface bacteria however to do their job efficiently, or so they have enough time relative to their numbers versus the amount of oxygen in the water, the flow on the outside has to be slow enough. If the flow is fast (> 50Gph) they can't strip the oxygen from water fast enough and thus the water that gets deeper still has oxygen in it.

That's the theory anyway... or what Seachem says in their write-up on de*nitrate... It sounds plausible, and if it is in fact what happens, then my question is, doesn't this also work the same way w/regular live rock?

Spacey

 

[keithhays]

I use the seachem Matrix which you have to use for higher flow and I have had really good success with it. I actually use the Pond size matrix for my 300 gallon system. I have about 5 gallons of Matrix which I believe is equivalent to about 250 pounds of live rock from a porosity stand point in a Reef Creations sump. It does appear to work the same as that amount of rock. I am adding a lot of fish so I will likely add another 5 gallons. This stuff is so porous it initially floats on water..its a rock that floats.

Most reef tanks are probably going to be in the "high flow" arena unless they are just really small, so the Matrix is going to work better.

I believe I am running approximately 800 gph through my sump. The matrix crosses the width of the sump its own specialize holding area, so the water can't bypass it.

 

[5pacey]

I did not mention Matrix, although I have been looking at it as well, because it is (they sell it as such) as you say for higher flow scenarios, and it doesn't have (as much?) capacity to perform denitrification compared to de*nitrate due to the former having larger pores. But, de*nitrate is suppose to have much smaller pores and thus be (as Seachem says) aimed at denitirification mainly. It will basically work the same as Matrix (not sure what it's efficiency is in comparison) with higher flow (>50Gph) but at slow speed it will provide optimal environment for denitrification.

They are both basically forms of artificial dry rock from the stand point of porosity, as are other materials from Eheim and dozen or so other vendors. They all claim to be superior due to massive amount of pores, their size, shape and other parameters I didn't even know applied to holes in a rock ...

My main point is that, while most sump systems and display tanks have flow much higher than 50Gph, thus would not work well for de*nitrate's claim to "fame", one could conceivably section off part of a sump, or even stuff a PhosBan reactor or similar w/de*nitrate or, if the same principle holds w/rock, rock rubble, set to 50 Gph and have themselves a de-nitrification filter at a fraction of a cost of other such devices sold for multiple hundreds of $... e.g. Koralin sulphur reactor etc.

Essentially, if the same principle holds, assuming what Seachem asserts is true, you don't need to get anything other than rock and just run water over it @ really slow speed to get it to do your de-nitrification. Such a section to work optimally, naturally, would have to follow the regular fast flow section (please ignore the disparity in flow for the sake of argument) which produces Nitrate as it's output.

I am am asking, postulating and deducing here in hope someone can point out a critical flaw ... or conversely, say that they did it and it works... and of course to induce others to think about this if they haven't already done so million times before.

Spacey

 

[keithhays]

I did not mention Matrix, although I have been looking at it as well, because it is (they sell it as such) as you say for higher flow scenarios, and it doesn't have (as much?) capacity to perform denitrification compared to de*nitrate due to the former having larger pores. But, de*nitrate is suppose to have much smaller pores and thus be (as Seachem says) aimed at denitirification mainly. It will basically work the same as Matrix (not sure what it's efficiency is in comparison) with higher flow (>50Gph) but at slow speed it will provide optimal environment for denitrification.

They are both basically forms of artificial dry rock from the stand point of porosity, as are other materials from Eheim and dozen or so other vendors. They all claim to be superior due to massive amount of pores, their size, shape and other parameters I didn't even know applied to holes in a rock ...

My main point is that, while most sump systems and display tanks have flow much higher than 50Gph, thus would not work well for de*nitrate's claim to "fame", one could conceivably section off part of a sump, or even stuff a PhosBan reactor or similar w/de*nitrate or, if the same principle holds w/rock, rock rubble, set to for 50 Gph and have themselves a de-nitrification filter at a fraction of a cost of other such devices sold for multiple hundreds of $... e.g. Koralin sulphur reactor etc.

Essentially, if the same principle holds, assuming what Seachem asserts is true, you don't need to get anything other than rock and just run water over it @ really slow speed to get it to do your de-nitrification. Such a section to work optimally, naturally, would have to follow the regular fast flow section (please ignore the disparity in flow for the sake of argument) which produces Nitrate as it's output.

Am am asking and postulating and deducing here in hope someone can point out a critical flaw ... or say that they did it and it works... and of course to induce others to think about this if they haven't already done so million times before.

Spacey

If I understand you correctly we are talking only about nitrate removal and not about anything else that you would need prior to or after for removal of other items. Also, if I understand the argument, any porous structure would work in a 50 gph scenario as well as de-nitrate?

 

[SantaMonica]

That material sounds a lot like "Filter Ag", which is sold by the cubic foot for water purifiers.

 

[keithhays]

That material sounds a lot like "Filter Ag", which is sold by the cubic foot for water purifiers.

I believe filter ag is a granular substance which would be problematic because it would act as more of physical filter even if the pore size and content were suitable.

 

[5pacey]

If I understand you correctly we are talking only about nitrate removal and not about anything else that you would need prior to or after for removal of other items. Also, if I understand the argument, any porous structure would work in a 50 gph scenario as well as de-nitrate?

Yes exactly. I am not touching on the nitrification part because that is well understood and used. Denitrification is trickier though and not easily achieved at volumes matching nitrate production thus most systems tend to be nitrate heavy or produce excess nitrate asa result of current filtration architectures applied most commonly. That is without any additional nitrate removing mechanisms such as sulphur reactors, biopellets, vodka dosing, water changes or algae reactors, refugiums with macro algae or mangroves.

Spacey

 

[AcroporAddict]

I have a 465 gallon BB SPS tank with a 155 gallon sump. The sump has a biochamber that I had about 5 gallons of regular matrix in. All water in the sump passed through the matrix, and was prefiltered by 100 micron filter socks. For the first several months the nitrate level was zero, but then started to creep up. I think the Matrix eventually gets coated with biofilm, so if you use Matrix I would periodically pull it and either rinse it or bleach/H2O2 it to get that biofilm off.

I pulled mine and now have a sulfur denitrator on the tank that is just now maturing. I'll see how this does vs the matrix and either leave the matrix out or reinstall it later.

Just FYI, there was a ton of mulm in the Matrix when I pulled it, even with 100 micron prefiltering.

 

[keithhays]

I love playing devils advocate. :smokin:

I think is general, you are correct, but some of your conclusions are not.

Whether you are using live rock, de-nitrate, matrix, sulfur, and in the vast majority of cases carbon dosing, you are essentially doing the same thing by different degrees. The same thing as it relates to nitrate is autotrophic denitrification.

De-nitrate apparently has an extremely small pore structure which in areas are able to produce low oxygen compartments that allows bacteria to consume nitrate. But, because the pores are so small that under high flow, the water just bypasses the whole structure and potentially making the de-nitrate just another surface for normal nitrification. This would make the preferred mechanism in microreefs where putting enough live rock for the same filtration would be problematic. It becomes a question of marketing to that segment of hobbyist. Actually having called them in the past on the question of flow and size, they definitely said, I should not use de-nitrate for my system as it would not work.

Matrix appears to have more complex structure capable of greater flow and able to catch the water, so to speak, at a high flow, but still complex enough internally to do de-nitrification internally and nitrification externally. Essentially, a more efficient live rock which would do the same thing, but with more mass. I think this product is attractive those of us who don't want to use live rock at all or at least not exclusively.

Of the three, live rock of course is the most variable and least consistent depending entirely on the variety, I also have a tank of Pukani which I believe to be more useful than say, a premium Fiji. Who is to say if I am right or wrong because someone will have 24" Fiji that weighs one pound. Either way, the rock is of no use without its holes for holding bacteria and filtering water.

Sulfur is merely live rock that happens to also be a food source in a low oxygen environment for denitrification. In many cases sulfur and (matrix or denitrate, or live rock rubble) are placed in with the sulfur as the real work is being done in the low oxygen environment and the sulfur is just the food source)

In all of the cases above, carbon dosing in addition with throw the process into hyper drive quickly (relatively speaking) reducing nitrate. (inject sugar water into your denitrator and watch is start producing sulfides on the grand scale)

There is a process by which carbon dosing will make the system heterotrhophically dominate, but that is usually secondary in a reef system except by accident. There are usually clouds of roaming heterotrophes as well as cyanobacteria as a result.

In short, I don't think seachem is selling anything that did not originate with the first person who discovered live rock could filter water, there are different tools that we use in different circumstances.

 

[keithhays]

I have a 465 gallon BB SPS tank with a 155 gallon sump. The sump has a biochamber that I had about 5 gallons of regular matrix in. All water in the sump passed through the matrix, and was prefiltered by 100 micron filter socks. For the first several months the nitrate level was zero, but then started to creep up. I think the Matrix eventually gets coated with biofilm, so if you use Matrix I would periodically pull it and either rinse it or bleach/H2O2 it to get that biofilm off.

I pulled mine and now have a sulfur denitrator on the tank that is just now maturing. I'll see how this does vs the matrix and either leave the matrix out or reinstall it later.

Just FYI, there was a ton of mulm in the Matrix when I pulled it, even with 100 micron prefiltering.

What size denitrator do you have?

I don't really have that issue with the Matrix, but I am week blowing out all my pumps, sumps, and pipes and as a part of that my Matrix gets blown pretty hard. I do expect that at some point because I am using the 200 microcron socks I will have to put them into a vat to de-sludge them with waste away, but I would do the same thing with live rock in my sump.

 

[wooden_reefer]

Denitrification in LR is said to be independent on the bulk flow rate outside.

Water experience friction and flow will slow in pores irrespective of the external flow rate.

It is possible that what deoxygenates the water to allow denitrification further into the pores is nitrification, to a great extent. So nitrification has to precede denitrification in a certain setup and the two processes most be in close proximity.

 

[JPMagyar]

If I may be so bold as to try and re-state the OP's question, . . .

. . . . is not the question:

Can Live Rock do the same job as Seachem's product without the need for said product?


If. . . and it's a big if . . . I have the question right than the answer seems exceedingly simple. Yes.

Live Rock, by means not fully understood allows for areas of low oxygen and as a result can act as as a nitrate removing factory. Is it as efficient as a purpose built system? No. Is Live Rock one of the foundations of successful aquariums? Yes. Do you need products like Seachem's product to have a successful tank? No.

Not sure what else folks need to know unless they just enjoy the underlying science


Joe :beer:

 

[5pacey]

Denitrification in LR is said to be independent on the bulk flow rate outside.

Water experience friction and flow will slow in pores irrespective of the external flow rate.

It is possible that what deoxygenates the water to allow denitrification further into the pores is nitrification, to a great extent. So nitrification has to precede denitrification in a certain setup and the two processes most be in close proximity.

Well... according to what Seachem says, and I am not saying I believe it 100% but don't have any other information at that level of detail, is that the reason why the flow needs to be <50 GPH, is that only at that speed the bacteria in upper layers conducting nitrification aerobically will have enough time to strip oxygen from the water and thus allow anaerobic conditions to form and denitrification to take place when that water gets deeper.

Conversely, if the flow is higher, nitrifying bacteria don't have enough time to use up all the oxygen during nitrification and because of this water deeper in the pores does not form anaerobic conditions, and thus continues to support nitrification, rather than denitrification, which would have only been possible if conditions were anaerobic.

So essentially, yes and yes to what you said... except that while technically denitrification is independent of waterflow, it really is indirectly dependent because of its dependence on how fast nitrifying bacteria use up oxygen in the water and flow speed of the water.

Spacey

 

[5pacey]

If I may be so bold as to try and re-state the OP's question, . . .

. . . . is not the question:

Can Live Rock do the same job as Seachem's product without the need for said product?


If. . . and it's a big if . . . I have the question right than the answer seems exceedingly simple. Yes.

Live Rock, by means not fully understood allows for areas of low oxygen and as a result can act as as a nitrate removing factory. Is it as efficient as a purpose built system? No. Is Live Rock one of the foundations of successful aquariums? Yes. Do you need products like Seachem's product to have a successful tank? No.

Not sure what else folks need to know unless they just enjoy the underlying science


Joe :beer:

So... yes that would be the basic question... however, one needs to be more specific because according to what Seachem says, you need water flow of <50Gph to achieve sufficiently anaerobic conditions deeper in the pores to provide conditions for denitrification. If water flow is >50Gph, then anaerobic conditions won't form and only nitrification will be taking place everywhere. Which is good too, but this will only increase the nitrification efficiency of the system, and will not support denitrification. Which, in turn results in a net production of Nitrate rather than aimed for net zero.

Then... there is also a question of efficiency of various substrates. As keithays mentioned Matrix for example is claimed to have a more extensive pore structure than rock and thus per pound can support more nitrification / denitrification (assuming the latter takes place). This in turn means that you may be able to get away w/a much smaller space to achieve the same filtration throughput. I don't know if 1) this is true, 2) if it is, then how much better is Matrix, or de*nitrate for example (or the 50 other substrates on the market) than rock (of which there is a wide range as well).

As far as what else do folks need to know... well, I would say that since majority of systems tend to be net Nirtate producers, and everyone agrees that it would be nice to change that so they are instead not producing any Nitrate, it would be beneficial to everyone to try and figure that out no?. In other words, to come up w/a natural way (without external reactors) to arrange your filtration system so that it 1) performs enough nitrification to take care of all ammonia generated by the system, 2) performs enough denitrification to take care of all Nitrate produced by the nitrification stage.

It seems, if one believes Seachem's assertion, that <50Gph flow will allow for increased denitrification to take place. What this in turn implies, to me at least, is that while I can't slow entire filtration stage flow to 50 Gph (or can I?), I could theoretically have a section, or a branch with a <50Gph flow... put rock or Matrix or de*nitrate or one of the other fake rock substrates there, and create a de-facto denitrifying stage. I could then vary the size of that and try to match it's throughput to the rate of Nitrate production and thus achieve a net zero Nitrate generation of the system. Which, I believe would make a lot of people happy.

Spacey

 

[WillM]

Hey 5pacey,
I have used both the Pond Matrix and the Denitrate. Both applications were on FW tanks. The Denitrate was used in an upflow reactor like you would use for GFO and I did keep the flow slow (<50Gph). I don't see how you would be able to regulate the flow without using a reactor. The Denitrate I used for months and honestly I think Seachem's claims are bunk. I never noticed a difference and still had to do massive weekly water changes to keep my nitrates within range. I no longer use it and notice no difference in the water quality now either. It might be a catch 22 that you have to limit the flow to <50Gph but at that flow rate it's not cycling enough water to keep up with nitrate production in the tank, but I used the recommended amount for my size tank, so I would have thought it would have eventually "broke in" and started reducing the nitrate levels. No such luck. I will endorse it for pouring under your tires when you get stuck in snow. I kept a gallon jug of it in my trunk for just that occasion and it worked like a charm.

However, that being said, and to show I'm not bashing Seachem, I am a big fan of Pond Matrix. But it is high flow and just good at the nitrification steps. The Pond Matrix I'm still using in my trickle filter on my 120G FW tank. Does a real good job of converting ammonia to nitrate. Other than that I'm still doing 30% WC on my FW tank to keep them happy.

 

[Nano sapiens]

While this type of product can have its uses in specific types of aquatic setups, in a typical reef tank the LR and LS, if kept clean, should be fully able to handle denitrification. Only in extremely high bio-load situations could one possibly see some issues.

I'm not saying that the product wouldn't perform it's intended function, but the end effect would just be added system complexity and cost.

 

[keithhays]

While this type of product can have its uses in specific types of aquatic setups, in a typical reef tank the LR and LS, if kept clean, should be fully able to handle denitrification. Only in extremely high bio-load situations could one possibly see some issues.

I'm not saying that the product wouldn't perform it's intended function, but the end effect would just be added system complexity and cost.

I think this may be the main question as their can be a significantly higher cost for live rock vs the other products given the amount of live rock needed vs an equivalent amount of the different seachem products. The OP specifically spoke about de-nitrate which is for small systems, but the same equation would play out with Matrix and then Pond Matrix. Even if in my case you are starting with dry rock, the amount of space required in my sump would the difference between filling my entire sump with rock vs what is about 1/5 of that space.