Sulphur in the reefaquarium

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Belgian Anthias

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In a normal aquarium without dosing and bio-filter: nitrification depletes alk but when that process takes place in a nitrifying biofilm the film will by nature also remove nitrogen due to the high oxygen consumption, about 16% of the nitrate production, which means each cycle +- 16 % of the nitrogen may be exported, without doing a thing. ( some claim a nitrifying bio-filter produces nitrogen!?)
If the nitrifying bio-film grows on a base of carbon carbonate most carbon will be retrieved from of the substrate dissolved by the acids . When growing on a base of carbon carbonate mixed with elemental sulphur more nitrogen gas N2 will be produced by the BADES process and exported, more accids will be produced, more carbon will be retrieved from the substrate dissolved by the acids. The effect on alk in the water column for both nitrification and dentrification will be minimal. Calcium and some sulphate is produced. Depending on the used substrate minerals are added, useful for calcification.
Each internal cycle of nitrogen, production, nitrification, consumption, production, nitrification a lot of the nitrogen will effectively be exported, this way restoring the nutrient balance as only nitrogen over-production considered not needed may be removed. Without doing a thing, just by nature! Naturally when no supplemental nitrogen is added. if the addition of nitrogen is adjusted to the removal rate, or vice versa, the removal rate to the addition, nitrate will not build up. One is able to manage both sides, the removal rate and the addition rate.

If all of the above is correct, the next question may be: why most reefers do not use a bio-filter?
 
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Dan_P

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Uh, no.

The conversion of the initial ammonia (it is ammonia, not ammonium) waste from organic metabolism into ammonia takes up alkalinity.
The use of that ammonium to remake organic molecules gives back the exact amont of alk.

It is a round trip from organics to ammonia to organics again. There's no way round trip processes can add or remove alkalinity.
Got it!
 
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Dan_P

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Sorry, No. That is incorrect.

I agree with the equations in your reference, and they are the same ones that I often use my articles. But you have misunderstood the processes involved. There is no net consumption of alkalinity.

Ebling et Al 2006:

https://cals.arizona.edu/azaqua/ista/ISTA7/RecircWorkshop/Workshop PP & Misc Papers Adobe 2006/7 Biofiltration/Microbial Floc Systems/2006 Aquaculture Stoichiometry of photo-auto-hetero - Ebeling.pdf

Equation 16 shows:


NH4+ + 1:18 C6H12O6 + HCO3- = 2:06 O2 --> C5H7O2N + 6:06 H2O + 3:07 CO2

" This equation predicts that for every g of ammonia– nitrogen converted to microbial biomass, 4.71 g of dissolved oxygen and 3.57 g of alkalinity (0.86 g inorganic carbon) and 15.17 g carbohydrates (6.07 g organic carbon) are consumed. Also 8.07 g of microbial biomass (4.29 g organic carbon) and 9.65 g of CO2 (2.63 g inorganic carbon) are produced"

This seems, at a first glance, to be consuming one unit of alkalinity (HCO3-) for each ammonia consumed), but that does not hold up to a deeper understanding of the processes involved.

The thing that you (and perhaps the author) are neglecting is that the nitrogen compound that is the product of metabolism by fish and other organisms is NOT NH4+. It is NH3.

The metabolism reaction is exactly the reverse of equation 3 in your reference. The product of the metabolism of organic matter with nitrogen in it is NH3. Of course, the reaction can be written as if it is NH4+, but when you do that, you necessarily produce alkalinity. That is what the reverse of equation 3 actually shows. Production of NH3 and then combination of that with some of the CO2:

NH3 + H2CO3 ---> NH4+ + HCO3-

And the reverse of equation 3 shows this "production" of HCO3- explicitly. Same for phosphate.

Consequently, the overall round trip from fish food to ammonia to production of biomass by consumption of ammonia to biomass formation with organic carbon has NO NET EFFECT ON ALKALINITY.

The same is true if you convert the ammonia along the way to nitrate. The overall round trip from fish food to ammonia to nitrate to production of biomass by consumption of nitrate to biomass formation with organic carbon has NO NET EFFECT ON ALKALINITY.
:)

Thanks!
 

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