Does LR reduce nitrates??

[Randy Holmes-Farley]

I couldn't preview the link, too risky to download onto phone wo knowing origins.


Based on what Lasse and others wrote, how do you square that article away with all the extra new things invented for nitrate control

In the 90s live rock and sand was claimed all that was needed

It's not an experiment that properly mimics a reef aquarium. It has simplified the study to the point where it would not be expected to work (due to lack of organic matter).

 

[Randy Holmes-Farley]

" IMO you have to choose – do you want have some NH4 content or some NO3 in the water column. I prefer fast nitrification in a biofilter and to handle the NO3 in another way.

FWIW, my point 5 doesn't really say it is desirable to not, only suggests that it happens (without experimental evidence aside from nitrate rising when many folks removed media like bioballs).

You must be the master of your own aquarium.

 

[Randy Holmes-Farley]

Here are the sections that show lack of any organics in the water. It is brand new seawater and nothing else!

Experiment with nitrate addition The preparation of seawater and tanks were as described in the previous section [I added this below]. Three experimental treatments were used for a total of six tanks. The baseline nitrogen concentration was created by adding 0.5 mL of 1 mol/L KNO3 (equivalent to 62 g/L NO3 – ) stock solution to the tank and LR was added to the experimental treatments 4 h later. Samples were collected every 4 h for 96 h. Water samples were filtered through a 0.45 µm microporous membrane and stored at –20°C. All water samples were analyzed using a flow analyzer (SKALAR SAN ++ Flow Injection Analyzer, Netherlands) after thawing.

Artificial sea salt (Blue Treasure, Qingdao) was diluted with deionized water to create artificial seawater with a salinity of 34. The prepared seawater was allowed to sit at room temperature for 24 h before use. Five liters of seawater were added to the experimental tank (20 cm×20 cm×20 cm), which was covered with clean plastic film to prevent contamination from air dust and then aerated. The tank was surrounded by thick canvas to protect from light. Three experimental treatments were used for a total of six tanks. Baseline nitrogen concentration was created by adding 0.5 mL of 1 mol/L NH4Cl (equivalent to 18 g/L NH4 +) stock solution to the tank. LR was added to the experimental treatments 4 h later. During the first 24 h, samples were collected every 3 h; after 24 h, samples were collected every 4 h for 72 h. An amount of 50 mL of water sample was collected each time, then filtered through a 0.45 µm microporous membrane and stored at –20°C.

 

[GoVols]

All I can say as one reefer is that after my own testing that I came to Randy's point #5 to my own reef with 1 gallon of Seachem Matrix at a 20 gph flow rate in it's own reactor.

Was not producing more nitrates but they were spewing into the open water column.

Just wanted to see if my Purigen reactor was making a difference and that it was working with my protein skimmer to remove organics before they hit the nitrogen cycle.

Gave it a good go and just went back to running the Purigen reactor as one piece to the larger puzzle

 

[Lasse]

I think they see the problem with their experiment:

"The denitrifying bacteria that play key roles in water treatment are mostly heterotrophic (Cai, 2008). In this experiment, the reason why LR lacks the ability to degrade nitrate may be due to the lack of dissolved organic carbon (DOC) as a reaction substrate and energy source."

Their experiment did not involve an operating reef tank (whether with extra dosed organic carbon, or that naturally there from organism and bacteria degradation of foods, etc.).

Really, I can't see how one would expect this to work without organic matter. The chemical equation for denitrification demands it:

organic + 124 NO3- + 124 H+ → 122 CO2 + 70 N2 + 208 H2O

It's like putting a mouse on Mars and saying, wow, it died, Mars doesn't support life. Maybe from lack of O2?

Agree but I´m still not convinced that your widely accepted point 5 is general true. Even if you have organic matter - it should be transported into the stones to anaerobic zones. In sand its another question because you will have organic matter there but you still need the transport of NO3 down there

My main objection is that I do not believe that there is any nitrification down 1 - 2 mm in the sand. All studies on nitrification biofilms shows that only some micrometres of the surface is active in the process. The nitrification process is highly demanding of oxygen level - less than 5 mg/l will hinder/slower the second step NO2 – NO3. The 100 %saturation of oxygen at 26-degree C in saltwater is around 7 mg/l. During daytime you will probably have this but during night time most studies shows a saturation level in well aerated (read well skimmed) system around 80% (in system with no fuge and no inverted lighting). 80 % saturation is around 5.6 mg/l and you will have less 1 – 2 mm down in the sand.

The lower level of oxygen in saltwater contra freshwater at the same pressure and temperature (its 1 – 1.5 ppm lower) is IMO the reason why it’s a slower rate of nitrification in saltwater.

However the findings that you sometimes will have lower NO3 levels if you do not have a bio filter is probably true but I have another explanation for this. You can probable see this in both sand based system as BB system. And IMO - the nitrification rate in LS is very poor.

The biofilm in a good nitrification reactor is thin, very thin. One of the most effective processes – the Kaldnes process is build on plastic parts that is in a very turbid environment mixed with air and water. The film is all the time very thin because of mechanical abrasion.

IMO the lower production of nitrate in skimmed system and no biofilter is not caused of transfer of nitrate down in the sand (and denitrification) but caused of bad nitrification rate, hence NH 4 in the water column and aeration out as NH3 in the skimmer. At pH – 25-degree C the NH4/NH3 ratio is around 94.6/5.4 % - at pH 8.5 its 85/15 %. The heavy aeration in modern skimmers can rise the pH locally in the skimmer during non-lighting periods – especially if you use CO2 scrubbers - and the result will be more as NH3 (the gas)

Of cause there can be another process taking place in the anoxic part of the sand bed that direct convert ammonia produced by bacteria to N2 through a process including NO2 – the anammox process. If this is the case – no NO3 will be produced. It shown from natural sediments in saltwater but as I know – never shown in aquaria but I´m convinced it exist in older aquarium with sand beds that haven’t been touched for many years

Sincerely Lasse

 

[GoVols]

Here is the BRS test and Ryan also killed the testing because the Pure Marine blocks were leaching aluminum into the water column from my memory ;Oldman.

Not a perfect test but all tanks came in at about 56ppm over the long haul.

 

[ChrisOFL]

Agree but I´m still not convinced that your widely accepted point 5 is general true. Even if you have organic matter - it should be transported into the stones to anaerobic zones. In sand its another question because you will have organic matter there but you still need the transport of NO3 down there

My main objection is that I do not believe that there is any nitrification down 1 - 2 mm in the sand. All studies on nitrification biofilms shows that only some micrometres of the surface is active in the process.

I took this picture from underneath my tank. My sand bed is 4inches deep so this is 4 inches beneath the surface, my sand grain size is about the same as sugar. As you can see it is abundant with life, different algae, bacteria, you can also see the worm/microfauna trails through the sand. The microfauna is what facilitates in the transport of water through the sand bed into the anaerobic zone. I would contend that there is nitrification and denitrification occurring throughout my sand bed.

 

[Lasse]

Do not misunderstand me - I run a DSB also and I run it with reverse flow - its for the denitrification and other anaerobic processes - not for nitrification because a sand bed does not give the environment for good nitrification whatever aquarium books say. But the question was about LS not sand beds.

But talking about sand beds – is there a nitrification rate worth to be mentioned. IMO not because the first critical surface for this to happen – the surface layers – is rather load with organic carbon and environment rich in organic carbon is by the book bad for nitrification to take place. There is other, fast growing bacteria, that dominate there.

I can show you a similar picture from my RDSB but both pictures is not how the sand bed looks like a couple of cm from the glass. The thin layer of the bed facing the glass is full of life because of algae (hence oxygen production) growing when its get light.

Sincerely Lasse

 

[ChrisOFL]

Do not misunderstand me - I run a DSB also and I run it with reverse flow - its for the denitrification and other anaerobic processes - not for nitrification because a sand bed does not give the environment for good nitrification whatever aquarium books say. But the question was about LS not sand beds.
But talking about sand beds – is there a nitrification rate worth to be mentioned. IMO not because the first critical surface for this to happen – the surface layers – is rather load with organic carbon and environment rich in organic carbon is by the book bad for nitrification to take place. There is other, fast growing bacteria, that dominate there.

I can show you a similar picture from my RDSB but both pictures is not how the sand bed looks like a couple of cm from the glass. The thin layer of the bed facing the glass is full of life because of algae (hence oxygen production) growing when its get light.

Sincerely Lasse

My point was more that I believe nitrification is able to penetrate much further down than just the top 1-2mm of a sand bed because of the microfauna moving it around constantly, creating channels for water to flow into, and could potentially be much more significant than even live rock because of potential surface area (this would vary depending on tank obviously). The picture I took is from the bottom of my tank, not the front glass, so I it leads me to believe that if enough nutrients can penetrate 4 inches of sand to grow algae from my refugium light then I do not see why nitrification would not be taking place at various depths within the DSB as well. Are you aware of any studies that show nitrification stops after the first 1-2mm? Because from my understanding, anaerobic bacteria (denitrification) would require at minimum an oxygen saturation of less than 1.5mg/l (about 8% or less).

 

[Randy Holmes-Farley]

FWIW, I'm not claiming that live rock is "great" at denitrification. Obviously, a lot of people see substantial nitrate despite having live rock.

I'm just not a fan of this published experiment to evaluate it.

I'm also not sure how much nitrification takes place in a typical established reef tank, and how much ammonia disappears from uptake and use in other ways (such as a source of N in photosynthetic organisms).

 

[Lasse]

There is a couple of thing talking against your theory about nitrification below the extreme surface of a sand bed.

First – oxygen levels. The nitrification process has an enormous demand of oxygen – for very NH4 converted to NO3 – you need 3 oxygen atoms. The bacteria itself need also oxygen for the growth and respiration. It has shown in thousands of studies of carrier for nitrification that the oxygen will only reach the first micrometres of the biofilm – after that its gone and used. This is from freshwater there the oxygen pressure is higher compared with saltwater. There is also competition according to oxygen from other types of bacteria – the heterotrophs – normal “break down of organic matter “bacteria

The second: The competition according space from the heterotrophs. These bacteria has a growth pattern that´s faster compared with the slow growing autotrophs (nitrification bacteria). A fast heterotroph double its biomass in 15 minutes – the nitrification bacteria can take 13 hours for doing the same. If there is organic carbon – the heterotrophs will kick out the nitrificators directly. Normally you have enough of organic carbon at the surface of a sand bed to have them growing unlimited. The use of dissolved organic carbon does not make the competition easier for the nitrificators. The nitrification bacteria do not need organic carbon for their growth – the use inorganic – mainly HCO3/CO3 that’s will be transferred to CO2 outside or inside the bacteria.

People that stir/clean the sand bed every day may lower the competition.

I know that my thought is not in line with the general idea among saltwater aquarists – but I have got my knowledge about these things from working in sewage plants, fish farms and different other applications that have nitrification as a major question. I have also work a little with denitrification and have some knowledge of this also – not in a theoretical way but in a practical way.

Your sandbed

IMO – the growth of algae in the bottom of your DSB as you show in the picture is not because of nutrients migrating from the water to the bottom of you DSB – the nutrients is produced of the breakdown process in the DSB of particulate organic matter.

That you get algae growing in the bottom is interesting but before I try to figure out the importance of this I have a question - Are you running the fuge light for 7/24?



Sincerely Lasse

 

[ChrisOFL]

There is a couple of thing talking against your theory about nitrification below the extreme surface of a sand bed.

First – oxygen levels. The nitrification process has an enormous demand of oxygen – for very NH4 converted to NO3 – you need 3 oxygen atoms. The bacteria itself need also oxygen for the growth and respiration. It has shown in thousands of studies of carrier for nitrification that the oxygen will only reach the first micrometres of the biofilm – after that its gone and used. This is from freshwater there the oxygen pressure is higher compared with saltwater. There is also competition according to oxygen from other types of bacteria – the heterotrophs – normal “break down of organic matter “bacteria

The second: The competition according space from the heterotrophs. These bacteria has a growth pattern that´s faster compared with the slow growing autotrophs (nitrification bacteria). A fast heterotroph double its biomass in 15 minutes – the nitrification bacteria can take 13 hours for doing the same. If there is organic carbon – the heterotrophs will kick out the nitrificators directly. Normally you have enough of organic carbon at the surface of a sand bed to have them growing unlimited. The use of dissolved organic carbon does not make the competition easier for the nitrificators. The nitrification bacteria do not need organic carbon for their growth – the use inorganic – mainly HCO3/CO3 that’s will be transferred to CO2 outside or inside the bacteria.

People that stir/clean the sand bed every day may lower the competition.

I know that my thought is not in line with the general idea among saltwater aquarists – but I have got my knowledge about these things from working in sewage plants, fish farms and different other applications that have nitrification as a major question. I have also work a little with denitrification and have some knowledge of this also – not in a theoretical way but in a practical way.

Your sandbed

IMO – the growth of algae in the bottom of your DSB as you show in the picture is not because of nutrients migrating from the water to the bottom of you DSB – the nutrients is produced of the breakdown process in the DSB of particulate organic matter.

That you get algae growing in the bottom is interesting but before I try to figure out the importance of this I have a question - Are you running the fuge light for 7/24?



Sincerely Lasse

The light is on for 16hours from the evening to next morning. If your saying the bio film is eating up the oxygen in the first few micrometers of its own film I could understand that but I do believe that the space between the sand grains along with the motion from the microfauna allows water to spread deeper throughout the sand bed more than we realize. This would mean the biofilm could grow in deeper regions because it would just be coating each individual sand grain not really forming a bacterial mat that covers the top layer of sand, depleting all the oxygen. From my understanding, if you disturb a DSB as part of your tank maintenance and don't allow the microfauna to flourish it is not going to function properly because the sand will not be getting moved around (I think you alternatively achieve good motion with your reverse filter setup). Nassarius snails and conchs are also a huge part of keeping a DSB turned over.

 

[GoVols]

I too used to run a DSB and when you see the bubbles coming up, then I always figured that it was gassing off the nitrates.

But, over time I would be scared to disturb the DSB for maintenance

Either way it's a great thread and we all find our ways. What works for one may not work for the other and "many ways to skin a cat"

Randy, Thanks for breaking down the OP's article.

 

[GoVols]

I took this picture from underneath my tank. My sand bed is 4inches deep so this is 4 inches beneath the surface, my sand grain size is about the same as sugar. As you can see it is abundant with life, different algae, bacteria, you can also see the worm/microfauna trails through the sand. The microfauna is what facilitates in the transport of water through the sand bed into the anaerobic zone. I would contend that there is nitrification and denitrification occurring throughout my sand bed.

Cronicreefer,
That some great live action in your shot

 

[ChrisOFL]

Cronicreefer,
That some great live action in your shot

Just check out those colors!

I get streams of bubbles that can last for a few minutes and I always figured it is N2 gassing off because it never releases any odor. Only ever happens at dawn which I always found a strange coincidence. Maybe it has to do with my refugium light and the growth on the bottom of the sand bed.

 

[rygh]

Why not? If nitrate is generated 1 or 2 mm down into a sand bed, it has a somewhat equal chance of drifting deeper for denitrification, or drifting out for entry to the water column. That doesn't happen on a bioball.

FWIW, many tanks do not have high flow everywhere.

So a question: Is it really an equal chance of Nitrate drifting each way?

If there is denitrification, the concentration of Nitrate would be lower inside
the rock than in the water column. So dispersion (as opposed to diffusion?) would say
that more Nitrate would head down into the rock.
On the other hand, with all the currents and so on, would that apply?

 

[Lasse]

Just check out those colors!

I get streams of bubbles that can last for a few minutes and I always figured it is N2 gassing off because it never releases any odor. Only ever happens at dawn which I always found a strange coincidence. Maybe it has to do with my refugium light and the growth on the bottom of the sand bed.

I´ll bet a penny that its oxygen produced by your algae in the bottom - they produce oxygen because of your fuge light.

Sincerely Lasse

 

[Randy Holmes-Farley]

So a question: Is it really an equal chance of Nitrate drifting each way?

If there is denitrification, the concentration of Nitrate would be lower inside
the rock than in the water column. So dispersion (as opposed to diffusion?) would say
that more Nitrate would head down into the rock.
On the other hand, with all the currents and so on, would that apply?

The net change of moving up or down depends only on the concentration of nitrate in either direction (assuming we are talking about diffusion and not convective flow). If it is the same, then the diffusion chance is equal. It will tend to move toward lower concentration. If there is flow, then it will move in the direction of the flow.