Sulphur media

[Belgian Anthias]

Using BADES is a very reliable way to control the nitrogen content of a system. No reactor is needed. And any container can be used as a reactor. One can make it as expensive as desired. Using BADES one does not need ORP reading, peristaltic pumps, or any other expensive devices which are only needed to solve problems created by using them. A BADES reactor is NOT kept anoxic!
A BADESS , once in balance, becomes self-regulating.

Using BADES, one may remove +- 3 gr nitrate/liter sulphur using a BADES reactor, 800 mg nitrate can be exported daily using 1liter sulphur having a removal rate of 100%, resulting in a 0 nitrate effluent.
The higher the supply, the higher the amount of nitrate that can be removed per liter of sulfur, but with a lower yield. With a supply of 4.5 grams / lS, the efficiency drops to + - 30% and about 1.5 g NO3 / lS can be removed. To remove 3gr NO3 per liter of sulfur, a very high supply is therefore required. ( Hignette1997) ref: https://www.baharini.eu/baharini/doku.php?id=nl:badess:hoeveel_zwavel

Basic rule for using a BADES reactor. This basic rule can also be used by "sulfur denitrator" users.

If the total volume of the system has to pass through the reactor once a day to be able to remove the daily amount of nitrate produced, then a 1% reactor is required. If only half of the total system volume is required, a 0.5% reactor is required. If the volume of the system has to pass through the reactor twice a day, you need a 2% reactor, or rather two 1% reactors. For example, a system with a nitrate level of 0.5ppm and a daily nitrate production of 0.4ppm will require a sulfur volume of at least 0.8%. A simple rule that is easy to apply and provides a trouble-free reactor. This rule can also be converted into a simple formula for calculating the necessary contents of the reactor (s). The volume obtained is necessary to have enough space to reduce the amount of oxygen supplied to such an extent that sufficient autotrophic denitrification can take place. (Matricaria2007 )
If the necessary parameters are not known, it is recommended to use a reactor with a content of at least 1%.
The basic rule applies when zero nitrates are pursued in the reactor output water, following the MAAO method. (CMF DeHaes2017)
ref: https://www.baharini.eu/baharini/doku.php?id=nl:badess:basisregel

All info needed is made available for those who are interested!

 

[Belgian Anthias]

I registered for that site. Its got some useful information. However, im not a scientific and converting things isnt my ability so I have to ask questions.

Personally i think a BADES system should be more common in our hobby. Why wouldn't we want to end the nitrogen cycle and gas it off? I think its easier than a few other nitrate removal methods, but it isnt very clear exactly what is needed to do. Neither is finding the sulfer media. I had to look all over my city and ended up having to order from another place at a cost of $125 for 5kgs.

So id need 13,350 grams of sulphur media to do a true bades system. I think ill start with 5kgs of media and see where that gets me.

I do not know as sulfur may have a different specific weight. The sulfur needed is calculated in volume, not in weight. As long there is enough.
Using BADES you may not be able to gas it off as for most applications the flow is high enough for N2 to be transported by the flow. If using a circulating pump this pump may not be the highest point.
Effluent water is always aerated before entering the main system.

My god, that is expensive. The pellets I use are +- 10$/kg, bought at a horticulture supplier in boxes of 10 kg. I was able to buy pure pipesulphur for < 5$/kg in sacks of 25kg. I have chosen to use pellets.
The best result one may have if mixing the media 50/50, but then it is more difficult to replace media. If using two reactors this is no argument as one may always keep one in service. Using aragonite, which dissolves better, there is a risk for clogging. Calcium carbonate media is used a lot faster as sulfur media. Calcium carbonate used in calcium reactors may be suitable. Remember, phosphorus is needed if you are going to target 0 nitrates in the effluent and commercial calcium reactor media may not contain much.
I use shell grit harvested from shell banks, at least a few thousands of years old, from before the industrial revolution. It is washed and heated before packing, to be used in chicken stables. It is available in different grain sizes.

 

[Lasse]

I´m not sure here - but can´t it be that way that it is there is a little bit of misunderstanding here. The daily production in Cory´s aquarium is not 150 ppm. It is his value just now. If he construct a BADES reactor large enough to take his daily production plus - let us say 5 ppm more. It will take some days before his down to 0 or 4-5 ppm but that´s IMO very good.

How to calculate the daily NO3 production? Here is a rough calculation. Cory use much algae product and they are normally rather high in proteins and the products in use are dry. The content of proteins in dry algae is around 12-35 %. Let us calculate with 25%. It means that of every 1 gram of products - around 0.25 g (250 mg) is protein. For each gram that is used as feed - 250 mg proteins is added to the aquarium. The N content in protein is in average 16% - this means that for each gram of food - 40 mg is pure N. If it is young and growing fish - around 20 % of this Nitrogen will be bond as fish biomass. - leaving 32 mg N into the water. Now not all of this N will be converted into NO3-N - some will be gassed off as NH3, some will be taken up as NH4 into algae and some will be collected in the skimmer cup as proteins or amino acids. Let us say that 50 % will be converted into NO3 (could be true - could be false). This means that for every gram of food - you will ad 16 mg NO3-N into the system -> it means around 71 mg as NO3. Now - Corys water volume is around 125 gallon -> 474 L. 71 mg in 474 L -> 0.14 mg/L (0.14 ppm) NO3 -

Summary - in this case - every gram of food added rise Corys 125 Gallon with 0.14 ppm NO3. If we calculate with worst case - all 40 mg N/gram food will be converted into NO3 - we will have a rise of 177 mg NO3 in 474 L -> 0.37 mg/L (0.37 ppm)

I have done this calculating after a tour on a electric bicycle of around 30 km - I do not guarantee that I have done the math right - but I think you understand the way of thinking.

Take a scale and take a weight of your daily feed (in gram) Cory and use my (between the thumb and index finger) calculation that you raise your NO3 level in your 474 L tank with between 0.14 - 0.37 ppm for each gram of food added.

If you get a figure of the daily load of NO3 in your system - I´m sure that @Belgian Anthias can calculate a proper filter for you. I understand that it must be a little bit larger than whats really is needed because the flow of 474 L/day (a single pass) means around 20 L/hour will contain around 7 mg O/L (140 mg/hour). In order to have the filter to work as a BADES filter (what I understand) - you need to bring down this to around 2-3 mg/l (40 - 60 mg/h) This means that at least 80 mg O/h must be consumed in the the first part of the filter by mostly heterophic bacteria. Correct me if I´m wrong.

Sincerely Lasse

 

[Cory]

Lasse, im away from home so ill measure my daily food tuesday.

I was thinking if magneisum carbonate or dolomite may work better in the reactor instead of calcium carbonate? This way youd get raising magnesium instead of calcium.

 

[Randy Holmes-Farley]

Lasse, im away from home so ill measure my daily food tuesday.

I was thinking if magneisum carbonate or dolomite may work better in the reactor instead of calcium carbonate? This way youd get raising magnesium instead of calcium.

That's likely a fine plan, but it will dissolve less readily.

 

[Lasse]

I was thinking if magneisum carbonate or dolomite may work better in the reactor instead of calcium carbonate? This way youd get raising magnesium instead of calcium.

That's likely a fine plan, but it will dissolve less readily.

Maybe a mix? You need the carbonate part in order to maintain the alkalinity and compensate for the losses during this type of sulphur driven denitrification (in opposite to a "normal" heterotrophic denitrification)

Sincerely Lasse

 

[Randy Holmes-Farley]

Maybe a mix? You need the carbonate part in order to maintain the alkalinity and compensate for the losses during this type of sulphur driven denitrification (in opposite to a "normal" heterotrophic denitrification)

Sincerely Lasse

Dolomite is calcium magnesium carbonate.

 

[Dkeller_nc]

Lasse, im away from home so ill measure my daily food tuesday.

I was thinking if magneisum carbonate or dolomite may work better in the reactor instead of calcium carbonate? This way youd get raising magnesium instead of calcium.

You can certainly do this, but I'd ask the question of how you normally maintain the calcium and alkalinity in your aquarium. If it's with 2-part dosing, compensating for the alkalinity-depleting effect of a sulfur denitrator is as simply as just upping the dosage of the alkalinity part.

You asked a few posts back why sulfur denitrators weren't more common in the hobby. They certainly were more common back in the late 1980's and early 1990's, especially with larger systems where large water changes were inconvenient and expensive.

Like every field, though, reef keeping has evolved through both scientific reasoning and experimentation. Encouraging bacterial reduction of nitrate to nitrogen gas through carbon dosing turned out to be far, far more convenient and just as effective as sulfur denitrators, and at far lower cost. There's also a lot less chance of poisoning the aquarium from an improperly run sulfur denitrator (or one that malfunctions).

 

[Lasse]

Dolomite is calcium magnesium carbonate.

Of course - I was only reading the first words

if magneisum carbonate

my bad

Sincerely Lasse

 

[Belgian Anthias]

I´m not sure here - but can´t it be that way that it is there is a little bit of misunderstanding here. The daily production in Cory´s aquarium is not 150 ppm. It is his value just now. If he construct a BADES reactor large enough to take his daily production plus - let us say 5 ppm more. It will take some days before his down to 0 or 4-5 ppm but that´s IMO very good.

How to calculate the daily NO3 production? Here is a rough calculation. Cory use much algae product and they are normally rather high in proteins and the products in use are dry. The content of proteins in dry algae is around 12-35 %. Let us calculate with 25%. It means that of every 1 gram of products - around 0.25 g (250 mg) is protein. For each gram that is used as feed - 250 mg proteins is added to the aquarium. The N content in protein is in average 16% - this means that for each gram of food - 40 mg is pure N. If it is young and growing fish - around 20 % of this Nitrogen will be bond as fish biomass. - leaving 32 mg N into the water. Now not all of this N will be converted into NO3-N - some will be gassed off as NH3, some will be taken up as NH4 into algae and some will be collected in the skimmer cup as amino acids. Let us say that 50 % will be converted into NO3 (could be true - could be false). This means that for every gram of food - you will ad 16 mg NO3-N into the system -> it means around 71 mg as NO3. Now - Corys water volume is around 125 gallon -> 474 L. 71 mg in 474 L -> 0.14 mg/L (0.14 ppm) NO3 -

Summary - in this case - every gram of food added rise Corys 125 Gallon with 0.14 ppm NO3. If we calculate with worst case - all 40 mg N/gram food will be converted into NO3 - we will have a rise of 177 mg NO3 in 474 L -> 0.37 mg/L (0.37 ppm)

I have done this calculating after a tour on a electric bicycle of around 30 km - I do not guarantee that I have done the math right - but I think you understand the way of thinking.

Take a scale and take a weight of your daily feed (in gram) Cory and use my (between the thumb and index finger) calculation that you raise your NO3 level in your 474 L tank with between 0.14 - 0.37 ppm for each gram of food added.

If you get a figure of the daily load of NO3 in your system - I´m sure that @Belgian Anthias can calculate a proper filter for you. I understand that it must be a little bit larger than whats really is needed because the flow of 474 L/day (a single pass) means around 20 L/hour will contain around 7 mg O/L (140 mg/hour). In order to have the filter to work as a BADES filter (what I understand) - you need to bring down this to around 2-3 mg/l (40 - 60 mg/h) This means that at least 80 mg O/h must be consumed in the the first part of the filter by mostly heterophic bacteria. Correct me if I´m wrong.

Sincerely Lasse

A BADES reactor must be a lot larger as theoretically needed for only reducing a certain amount of nitrate. One must minimal be able to remove the daily overproduction not only at the high starting level but also at the desired low level by which the reactor must be big enough to handle the flow needed, including the DO entered, while maintaining sufficient denitrification capacity.

If more as the daily nitrogen overproduction is removed daily, the level descends. If the level descends, maintaining the same flow means less nitrate is entered lowering the nitrate removal rate. This may go on until the reactor turns into an HS and ammonia factory or until the critical level is reached, the removal rate becomes too low for exporting more nitrate-nitrogen as produced daily. To prevent this the reactor must be big enough and the flow increased in function of the desired nitrate removal rate.

It is difficult to base the average daily nitrogen overproduction only on the food added, also internal produced food is used and remineralized, while the skimmer stays active. The removal rate of organics partially remineralized, of TOC and DOC, by the skimmer is not known and may be variable.
The C/N ratio of the food added, the protein content, will also have an influence on the nitrate production. Using low protein food results in less nitrate production.
But it is a good starting point for managing the nutrient content in the system, knowing what is added.

As explained , it is advised measuring the average daily nitrate overproduction over at least a week's time before starting using BADES or before using any other method for removing safely stored nitrate-nitrogen. This knowledge may overcome overdosing or overdoing it. It is just for having a base to start with and which can be used for applying the basic rule to determine the volume minimal needed. I advise using a reactor bigger as needed which makes the system future proof.
It is not difficult to calculate the minimal quantity of sulfur needed to export a certain quantity of nitrate-nitrogen, but this is not how it works as one must take into account the space needed for aerobic remineralization and nitrification, to consume oxygen entered and maintain the nitrogen export ratio needed.
There is a good reason why M.Longouet advised to use a1% sulfur to reduce a nitrate level of 50ppm and 2% for reducing a nitrate level above 50ppm and that has nothing to do with the nitrate level itself but with targetting 0 nitrate in the effluent.

I was thinking if magneisum carbonate or dolomite may work better in the reactor instead of calcium carbonate? This way youd get raising magnesium instead of calcium.

Before starting using BADES I only can advise you to ask your self why the nitrate level has increased and total nitrogen consumption is low. Once using BADES you will not be able anymore to use the evolution of the nitrate content for managing the system, the evolution of nitrate production is often the messenger, killing the messenger will not remove the underlying problems causing the nutrient imbalance.

It is not my decision, I only can advise starting by following the basics. Calcium is not a problem in a reef aquarium, you may always add some dolomite later or make corrections if needed. Adding dolomite increases the risk for clogging of the media.
It has been reported plaster may be produced, depending of the calcium carbonate media used.
It has also been reported most sulfate produced is removed when renewing the calcium carbonate media, maerl was used.

As I understand you are using a bare bottom, which means most nitrate production has depleted system alkalitity.
If BADES is used flowing the basics, nitrification, and or autotrophic denitrification will add calcium but will not affect alkalinity much, some bicarbonate may be added.

Starting using a BADES biofilm reactor will redistribute the nutrient content in the system.

 

[Belgian Anthias]

Final contribution.

To lower the nitrate level one has to remove a bit more like the daily nitrogen overproduction. Using BADES one may not only remove NO3-N entered but also a lot of NH4-N. Using BADES one may overdo it, and remove a lot more as needed. Keeping a NO3-N reserve is essential.
It is the intention to start with a reactor that is big enough to handle the flow needed to remove daily the daily nitrogen overproduction once the desired nitrate level is reached, by exporting NO3-N + NH4-N entered . But one may always add media or install a second reactor.

Theoretically, one only needs 1l sulphur for removing 800mg nitrate daily at 100%. At a level of 150ppm and targetting 0 nitrate in the effluent 1 liter may remove a daily overproduction of 1,6 ppm which may be enough for lowering the level. the flow will be +- 6 liters/day. If 2 liters sulfur is used, using a BADES reactor may remove max +- 1500mg/day at a flow of +- 14l/day. If 5 liter sulphur is used one may remove +- 3500 mg/day have a flow of +- 35 l daily. The level may descend very fast but also the removal rate if 100% effectiveness is targetted. If the daily nitrate production rate is known we now are able to calculate at what nitrate level the critical point of the reactor will be reached. Using 5 liters sulfur, having a flow of +-35litre daily ( targetting 100% effectiveness) one still may be able to remove the daily overproduction at a level of 20ppm as theoretically 700mg nitrate can be removed daily wich is +-1,4ppm daily in a 500l tank. Somewhere between 20 and 10 ppm probably the reactor will not anymore be able to lower the nitrate level. This is the critical point of the reactor kept at 100% effectiveness.
In practice one must be aware only < 1/5 of the max capacity is used at that moment and all nitrate entered is used up long before the HRT ( Hydraulic retention time) and this will cause the need for another oxygen source, being sulfate, resulting in producing HS and ammonia, remineralizing the dying biomass not being able to use nitrate and or sulfate.

To prevent all this a BADES reactor is managed differently and the flow is maximized in a way still 100% of the nitrate entered may be removed but the reactor is not kept + 90% anoxic to become 100% effectiveness. By Increasing the flow long before the critical point is reached the removal rate can be kept high enough but also increases the space needed to consume oxygen which will fill up space not needed for denitrification, limiting sulfate reduction. The reactor must be big enough! If the reactor is big enough, in practice the reactor is easily managed as one only has to target about the same nitrate content in the effluent until the desired level is reached. A BADES reactor needs a lot of attention during the period of decreasing the level for increasing the flow, certainly if the initial level was very high. Once the desired level is reached and the reactor has found its balance it will become self-regulating. IF IT IS BIG ENOUGH! Depending of the daily nitrogen overproduction to remove daily a small reactor may be big enough. A BADES reactor which is big enough may handle a flow of 2x the system content daily having 0 nitrate in the effluent

Using a BADES biofilm reactor it is the other way arround.
We first install nitrifying biofilms, it is a normal bio-reactor or -filter. It will contain all bacteria needed, +-40% of bacteria present in a healthy nitrifying biofilm follow an anaerobic pathway, including the sulfur bacteria needed. Once the reactor is conditioned the flow is slowly reduced. Once conditioned the effluent will probably contain more nitrate as the influent, depending on the ammonium reduction rate, a nitrifying biofilm may export +- 15% of the nitrogen processed within the biofilm without interfering.
The flow is slowly reduced until the effluent contains less nitrate as the influent. After each correction, one has to wait a few days for the result.
If the level does not descend after a few days the flow is decreased a bit more, increasing the difference between effluent and influent. It is the intention to remove daily a bit more like the daily nitrate overproduction. As less amonium can be used in the system more nitrate will be used as a nitrogen source, slowing down growth rates and lowering the level, slowly.
For those who want to spent money, the DO in the effluent may be as low as 2ppm or as high as 2ppm, as you wish, to maintain max nitrification/denitrification ratio.

A BADES System is based on enough nitrogen production to keep everything going, a BADESS is not what is needed for an LNS or VLNS.

Using BADES is not my preferred method for managing the nutrient content but it is my opinion the best way for restoring the nutrient balance and for exporting nitrate if a high and effective export rate is needed. Using BADES provides full control over the nitrogen export rate and over the nitrate level and is, therefore, the only method giving the user the possibility to effectively manage the nitrogen content as desired.

There is no need for a reactor for applying BADES

 

[Lasse]

It is difficult to base the average daily nitrogen overproduction only on the food added, also internal produced food is used and remineralized, while the skimmer stays active. The removal rate of organics partially remineralized, of TOC and DOC, by the skimmer is not known and may be variable.

IMO - it is the only way of determine the load. Even if the internal loops may alter the production in single day - the average load is total determined by the input in the system. Rest is only time depended altering of internal load.

As long as there is nitrate in the water - there will be no important production of hydrogen sulphide - therefore - I would aim for around 2 ppm NO3 in the effluent.

Sincerely Lasse

 

[Belgian Anthias]

IMO - it is the only way of determine the load. Even if the internal loops may alter the production in single day - the average load is total determined by the input in the system. Rest is only time depended altering of internal load.

As long as there is nitrate in the water - there will be no important production of hydrogen sulphide - therefore - I would aim for around 2 ppm NO3 in the effluent.

Sincerely Lasse

Lasse,

To have a guideline of the average nitrogen overproduction we advise to take a nitrate reading in the morning before lights on and again at least 7 days later at the same moment.

Do not mix up the nitrate content in the system water and the nitrate availability in the reactor as nitrate and other nutrients may be used up very fast in a reactor. Also in a biofilm, the situation will be completely different .. Keeping a reserve may tell us a situation of insufficient availability may be corrected fast but the time needed depends on the local water exchange rate and the local consumption rate which involves passing layers and many different situations, including flow management. Keeping a reserve will prevent long term starvation, causing problems.

Using BADES there will never be important HS overproduction as always sufficient nitrate will be delivered, nitrate may be produced in the reactor and will be available in the outer layers of the biofilm. In zones where sulfate reduction takes place, which is not avoidable, it takes place in every nitrifying biofilm, the produced HS may be used for autotrophic denitrification in OMZ zones, producing sulfur or sulfate, depending of the nitrate availability. As the effluent still may contain DO, any HS not used for denitrification will be removed when leaving the biofilm. As the effluent of a BADES is always aerated the risk is nihil.

Keeping +-2ppm DO in the effluent ( +6ppm DO in the influent) permits full autotrophic denitrification and nitrification (HwangEnCo2005)) which was already known in the nineties. But this must not be targetted, otherwise, some users may actually buy an expensive DO meter which is not needed. 2ppm DO must not be focussed as the goal is removing the daily nitrate overproduction daily, not trying to keep exactly 2ppmDO in the effluent, something which also will limit flow management, as is the case using an anoxic kept "sulfur denitrator". Having full control over the nitrate removal rate is what it is all about, not targetting specific parameters.

A mixed reef aquarium has a very low bio-load compared to an aquaculture system and there is absolutely no reason for trying to maximize the efficiency of processes as this will limit the possibility for managing the export rates as desired.

In my opinion, a reef aquarium benefits the most by having a very low DO content, not by selective removal by a skimmer or GAC, but by a very effective remineralization capacity. Then we reuse the produced building materials to produce food, using light energy, closing the food chain. The nitrate or and phosphate level does not influence growth rates and does not harm corals. But all may be reused and recycled, making a choice between feeding the end-users directly or indirectly or a mix of both.

 

[Lasse]

Do not mix up the nitrate content in the system water and the nitrate availability in the reactor as nitrate and other nutrients may be used up very fast in a reactor. Also in a biofilm, the situation will be completely different .. Keeping a reserve may tell us a situation of insufficient availability may be corrected fast but the time needed depends on the local water exchange rate and the local consumption rate which involves passing layers and many different situations, including flow management. Keeping a reserve will prevent long term starvation, causing problems.

Instead of talking about NO3 - we should talk about the N flux through the system - in one or another form. and the N can´t just show up like with help of the philosophers stone. It can disappear from the ecosystem (the aquarium) in its volatile forms (N2, NH3 and NOx) but it can´t just show up. The N load in the system is 100 % related to the outside food addition.

Sincerely Lasse

 

[Belgian Anthias]

Instead of talking about NO3 - we should talk about the N flux through the system - in one or another form. and the N can´t just show up like with help of the philosophers stone. It can disappear from the ecosystem (the aquarium) in its volatile forms (N2, NH3 and NOx) but it can´t just show up. The N load in the system is 100 % related to the outside food addition.

Sincerely Lasse

As the different nitrogen sources are decisive for possible toxicity, growth rates and alkalinty changes I will continue to name the different nitrogen compounds, although for easy calculations, and to compare, one can use NH3-N, NH4-N, NO2-N , NO3-N. etc.
N2 can be fixed by many with cyano on the first row, they are part of most mini ecosystems, microbial communities, coral holobionts and of course are an important member of phytoplankton and a basic food source. But they also prefer NH4-N as a nitrogen source. Maybe 100% needs a correction?

 

[Cory]

So ive measured my daily food input with just dry food. Its approximately 4.1 grams a day.

 

[Cory]

You can certainly do this, but I'd ask the question of how you normally maintain the calcium and alkalinity in your aquarium. If it's with 2-part dosing, compensating for the alkalinity-depleting effect of a sulfur denitrator is as simply as just upping the dosage of the alkalinity part.

You asked a few posts back why sulfur denitrators weren't more common in the hobby. They certainly were more common back in the late 1980's and early 1990's, especially with larger systems where large water changes were inconvenient and expensive.

Like every field, though, reef keeping has evolved through both scientific reasoning and experimentation. Encouraging bacterial reduction of nitrate to nitrogen gas through carbon dosing turned out to be far, far more convenient and just as effective as sulfur denitrators, and at far lower cost. There's also a lot less chance of poisoning the aquarium from an improperly run sulfur denitrator (or one that malfunctions).

I normally maintain with limewater. But i have the capability to use two or three part too.

Ive tried voda and vinegar but never seen a reduction in nitrates.

 

[Cory]

So im adding approximately 1.5 ppm no3 per day as a max

 

[Cory]

That's likely a fine plan, but it will dissolve less readily.

Do you think it will still neutralize the effect of the sulphur denitrator though? How could I make this work?

 

[Lasse]

Maybe 100% needs a correction?

Let us say 98 % instead

Your right - N fixation is one way - and in nature it is seen as the most important N source for marine production - however in an aquarium I will still say that it is a very minor pathway for N to enter the aquarium compared with nature. In one recent study it was found that the daily N-fixation in the north sea could be as high as 96.7 nmol N/L and day. For us it means around 0.001 milligram N per L and day (or roughly 0.001 ppm) As NO3 it will be around 0.003 ppm. I hope I have done the right math here. Compared with @Cory calculation of max 1.5 ppm a day from food

I do not think that N fixation is higher in our aquariums compared with nature because the major N fixation guys in nature is planktonic cyanobacteria - and I do not think they are common in our aquarium.

I´m not saying that my calculation of daily N contribution is rocket science - it is a very rough example but tell us in which county we are in at least

Sincerely Lasse