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Cultivated Reef

Dosing Nitrate / Nitrogen on purpose?


uglyfish

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I've read in more than a few instances people dosing nitrogen to their tanks in order to reduce phosphates.

 

The Redfield Ratio finds that carbon, nitrogen and phosphates exist in certain ratio in ocean planktonic life, dead or alive. And that ocean ratios echo those ratios levels found in marine plankton. Carbon:Nitrogen:Phosphorous in ratio 106:16:1

 

What we see when carbon dosing with simple vinegar, vodka or biopellets is typically a good reduction in no3, followed by a reduction in po4, then a continual slow rise in po4. This is not everyone's experience but it is mine and I've read other instances that match my experience.

 

The theory is that no3 is reduced to the point where po4 reduction stops. The Redfield ratios state that consumption of no3 to po4 is 16:1. If you don't have a 16:1 no3:po4 ratio, po4 reduction stops. And once no3 is depleted, po4 will rise. And until the ratio is corrected, po4 will continue to rise.

 

Therefore, dosing nitrate, where nitrate is limited, would help to reduce phosphate.

That's what I've read and that's the theory.

 

Products like Red Sea's Nopox and Zeostart are very good at reducing both no3 and po4. Seemingly better than straight carbon or biopellets. I'm wondering if they contain some amount of nitrogen to help balance this ratio.

 

Is anyone here dosing nitrogen for this express purpose?

I'm curious about outcomes and dosing amounts.

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altolamprologus

I dose potassium nitrate on my macro algae tank. Even with feeding a lot, nitrate stays at zero while phosphate rises because there isn't enough nitrate for the algae to grow, exactly what you're describing. I've been considering dosing it in my reef to give my chaeto a boost to help reduce phosphate

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I have the same problem in my macro algae tank - I never thought this same principle applies there. If the redfield ratios are universal, then macros would be consume no3 and po4 in the same ratio too... how about that.

 

Can you tell me more about how much and how often you're dosing? Also, what were your po4 levels before and after you started dosing?

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I have done this in the past on an NPS tank. I used sodium nitrate, but potassium nitrate will work just as well. I added the equivalent of 1mg/L of NO3 per day and it worked quite effectively to bring the phosphate down below 0.10 mg/L.

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I have done this in the past on an NPS tank. I used sodium nitrate, but potassium nitrate will work just as well. I added the equivalent of 1mg/L of NO3 per day and it worked quite effectively to bring the phosphate down below 0.10 mg/L.

 

I knew you would know! Thanks.

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Products like Red Sea's Nopox and Zeostart

 

I was looking at the ingredients list for one of these products the other day. I forget which brand: Methanol and Acetic Acid. Why pay so much for that in a bottle? :D You can get a gallon of vinegar for a couple bucks at the grocery store...

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I was looking at the ingredients list for one of these products the other day. I forget which brand: Methanol and Acetic Acid. Why pay so much for that in a bottle? :D You can get a gallon of vinegar for a couple bucks at the grocery store...

 

I diluted zeostart with rodi water 5:1 and tested my theory with the salifert nitrate test kit...

 

post-70116-1340865166_thumb.jpg

 

Zeostart contains nitrates! Vinegar and nitrate - $45.99!

 

Zeostart did lower my phosphate more than biopellets alone. I wasn't imagining it and it's because it contains extra nitrate. Since I've already dosed nitrate (without knowing it) I guess I can save my money and just add nitrate. The theory checks out... let the nitrate dosing begin.

Edited by uglyfish
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  • 1 month later...

I've been nitrate dosing for a few weeks now, no gfo, 0.3mg/l nitrate, daily.

Cyano started all over within 3-4 days, it lasted just over a week and receded rather quickly.

No3 now reading less than 0.02, Po4 0.01. Still feeding 3x daily heavy.

I am really amazed at the nitrate reduction of the biopellets.

 

I had a friend check Red Sea's Nopox carbon product for nitrate - it doesn't seem to contain any.

The label says it contains methanol and acetic acid, but it has an overwhelming smell of acetone (nail polish remover). My friend swears by this stuff for both no3 and po4 reduction and his tank is looking good.

He doesn't dose daily - maybe once or twice a week as required. He doesn't run gfo and keeps po4 at 0.01.

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  • 2 weeks later...
I was looking at nitrate dosing, but I don't know if the cyano all over is something I could deal with.

 

I just purchased a bottle of sodium nitrate from Ebay to start nitrate dosing on my clam quarantine tank. Not really concerned about cyano in a QT, but do run phosguard.

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I was looking at nitrate dosing, but I don't know if the cyano all over is something I could deal with.

 

Huh? There's no reason adding inorganic nitrate to your water will cause cyano to grow if it's not already.

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Where are you getting ur nitrate for dosing?

 

Seachem Flourish Nitrogen. I dosed about 10-15 drops / day.

 

Huh? There's no reason adding inorganic nitrate to your water will cause cyano to grow if it's not already.

 

There's always more to the story... I also run biopellets and am feeding heavy. In the last week, cyano has ravaged my tank - sand, glass, rocks. I assumed it was the nitrate dosing that caused the cyano because I had been feeding heavy for some time, without a cyano problem. The overfeeding probably just caught up to me.

 

I've had the biopellets running 3 or 4 months now. They pull down nitrate very efficiently, but at a cost. My corals were getting very pale, stn started. So to compensate for the lack of nutrients, I fed heavily, which probably led to higher DOC, which probably fueled the cyano.

 

The nitrate dosing experiment worked in showing that adding nitrate, where nitrate is 0 and phosphate is higher, while carbon dosing, will reduce phosphate. I don't know if nitrate dosing is especially good for the overall health of the tank though... it just seems to reduce po4, where no3 is limited.

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http://wardsci.com/product.asp_Q_pn_E_IG0015554

 

A 100g bottle would be sufficient for pretty much anybody.

 

If you dissolved the entire contents of a 100g bottle ($7.15) into a 1L bottle of deionized water (an old rinsed out gatorade/soda bottle will work), you'd have a 100,000 mg/L solution of sodium nitrate.

 

Sodium nitrate is 73% nitrate by weight, so that is a 73,000 mg/L solution of nitrate.

 

If you wanted to raise the nitrate concentration by 1 mg/L daily in a 10 gallon tank (38 L), then you would add about 0.5 mL of this solution to your tank every day. This is about 10 drops, more or less, and your 1L of stock solution would last you about five and a half years with daily additions.

 

It's a rough way to make a stock solution, but plenty accurate for our needs. If you end up erring by 20% in either direction it is not really a big deal. As always, test your water and watch your animals to guide your dosing. :)

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Omg thanks wombat! I forgot all my chemistry math junks. Perfect!

 

I actually just ordered 1lb of sodium nitrate on ebay 99.6% pure. Hopefully it isnt bullsh!t.

 

Im sure its more than i need so if anyone needs some. Pm me and ill send you a little of it

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Thank you. Too much will result in browning of corals, correct?

 

I dosed very little, 0.3mg/l... my only goal was to balance out no3 to po4. I would be careful dosing 1mg/l daily unless you're denitrifying strong and po4 is high. (you still have the regular nitrate sources with feeding). Watch your sps closely - you will notice a colour change in the skin within days - if the corals get too dark, I would ease off.

 

Also - the 16:1 ratio I quoted in my first post isn't really accurate for this application. As I read more - It's much much more complex than that. It depends on many variables and while there is some ratio of C:N:P consumption, 106:16:1 probably isn't correct for this application. Also - apparently sulphur plays a role as well. I'm reading up on stoichiometric ratios but I can't understand most of it too good - I have to wikipedia every third word. Fascinating stuff though.

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  • 3 months later...
gaberosenfield

Interesting info in this thread, thanks! I am about to start dosing KNO3 in my 20 gallon, which I have been carbon dosing with my own home made carbon mix (a modified vodka+sugar+vinegar mix). I consistently read zero nitrates with my API test kit and somewhere between 0 and 0.25 ppm phosphate. Obviously these are not very accurate measurements; I have not used a more accurate test like a hanna checker. I will post my progress here.

 

BTW, there are multiple threads on dosing inorganic nitrogen over at algaescrubber.net. They are using algae to absorb the nitrogen rather than carbon dosing and skimming, but the same ideas should apply. One guy even has an ammonia dosing system! :eek:

Edited by gaberosenfield
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  • 2 years later...

Very cool thread that was great to read. I have bumped into other threads that have talked about dosing nitrate to ULNS systems that have PO4 that doesn't go down.

 

I know this thread is old but I would love to hear from others that have a little more info. I am currently dosing 10 drops per day of Seachem Flourish Nitrogen due to pale colors in my 3 year old 34 gal reef tank full of sps. I think I am a little too aggressive in keep it clean and colors are nice but not quite happy with them. I will try to remember to update on here.

Apologize to the OP for the hijack, hope they chime in.

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Here's a RedSea opinion piece to chew on:

 

 

Nitrate and Phosphate Reduction via Carbon Dosing
By
Sharon Ram
Chief Scientist, Red Sea

Fighting nutrient build up in the aquarium is one of the major struggles the common hobbyist must face on a daily basis. Today, there are several methods to reduce nutrient levels; some by resins (ad/absorbers) and other chemical filtration components, but the latest trends include “pro-biotic” and/or the enhancement of biological nutrient reduction by bacteria.

Most hobbyists that favor biological filtration are well aware that the limiting factor in these processes is the absence of low molecular weight carbon compounds, which act as the energy source for the reduction processes. In order to boost the biological activity, many hobbyists started to dose the tank with any available carbon sources such as vodka, vinegar and sugars or various mixtures of all three. Common knowledge suggests that by providing enough organic carbon sources, together with the availability of the anoxic areas in the tank (live rocks and sediment) will be enough to encourage proper denitrification and phosphate reduction activities. Theoretically this is true, however it may also encourage other biological activities that may lead to disaster if they are not controlled or prevented from becoming established. It is important to be aware that the dissimilation processes in the marine environment involves very complicated ecological interactions between several groups of bacteria. These groups include 2 groups of dissimilatory nitrate reducers, another group of POA’s (phosphate accumulating bacteria or PHA bacteria) and the SRB’s (Sulfate reducing bacteria).

Between these 4 groups there are continuous competition and inhibition relationships that are regulated by the concentrations, availability and ratios of nutrients (nitrogen, phosphorus and sulfur), the availabilities of enzymatic co-factors and other biotic and abiotic factors.
When we investigate the dissimilatory pathways in the aquarium, we found the two major bacterial groups, the first group is the DNRA bacteria that reduces nitrate to either nitrite or ammonia, and the other group of heterotrophic denitrifiers that reduces nitrate via nitrite to gaseous nitrogen. Elemental nitrogen is the end product of this process, but intermediate accumulation of nitrite, nitric oxide and nitrous oxide may take place under certain conditions, usually in the absence of enzymatic co-factors.

Environmental factors, in particular the availability and type of organic carbon compounds, the C/N ratio, the availability of specific co-factors and the oxidation/reduction state of the aquatic environment, dictate to a large extent the occurrence of each dissimilatory group and the primary reduction pathway.
For example; an unbalanced C/N ratio will prevent full denitrification and will increase DNRA activity which leads to the accumulation of ammonia and nitrite. After the initial maturation cycle most hobbyist do not test for NH4+ and NO2- and therefore while dosing carbon sources they may observe a reduction in NO3- but will not notice any accumulation of ammonia or nitrite. Even when the C/N ratio is optimal for denitrification there are other obligatory factors that regulate the full denitrification of nitrate to free nitrogen.
These factors include specific chemical elements that act as co-factors in each stage of the denitrification process. The absence or unbalanced levels of these elements may end the denitrification process in any of the early stages and will lead to the accumulation of toxic N2O and NO.
Therefore, one of the important aspects of biological nutrient reduction is to encourage specific dissimilatory pathway of heterotrophic bacteria and to ensure a complete process. This is what Red Sea’s NO3clear.pngO4-X was developed for.

Red Sea’s NO3clear.pngO4-X provides stoichiometricaly balanced levels of several carbon compounds, which we found encourage heterotrophic denitrifiers upon the DNRA bacteria and by that it prevents the accumulation of ammonia or nitrite. NO3clear.pngO4-X also provides 7 enzymatic co-factors to insure complete denitrification to nitrogen gas and prevent the probability for N2O and NO formation.

Usually under denitrifying conditions with the availability of a sufficient carbon source, another 2 groups of nutrient reduction bacteria will start to thrive; the poly-phosphate accumulating bacteria and the sulfate reducing bacteria. These two groups have significant impact on the overall nutrient reduction processes in the aquarium.

The most common PAO’s or Poly-P bacteria are the PHA’s that accumulate phosphate in a two stage process of aerobic / anoxic and anaerobic conditions. These bacteria compete with the denitrifiers for the carbon source and in anaerobic conditions they may release PO4-3 back to the water. We have found that specific strains of heterotrophic denitrifiers are capable of accumulating phosphate and synthesize poly-P during the process of nitrate reduction with nitrate instead of oxygen serving as the terminal electron acceptor, so the double stage of aerobic/anoxic becomes irrelevant. When the bacterial population proliferates, bacterial flocks released to the water column are then taken out by the skimmer and therefore phosphates are stripped out of the system.

Red Sea’s NO3clear.pngO4-X, encourages the proliferation of heterotrophic denitrifiers that have the biological capability to synthesize poly-p in anoxic conditions (that can be called PHB) upon other PHA bacteria by maintaining balanced reduction of both nitrate and phosphate. Rapid reduction of nitrate over phosphate will lead to a rapid proliferation of anaerobic PHA bacteria and cyano-bacteria outbreak that can assimilate atmospheric nitrogen to thrive.

The fourth group of bacteria is the SRB, these bacteria reduce sulfate to toxic sulfide in anaerobic conditions. Since sulfate is present in seawater at levels around 940 ppm, and carbon source and anaerobic conditions are also available, nothing can prevent sulfide production.
The proliferation of SRB’s will affect the other bacterial groups by competing for the carbon sources and by inhibiting their activities due to the toxic sulfide they release.
During our research we have found 3 elements that can inhibit the activity of SRB by competing with sulfate and breaking the intracellular respiratory complex thereby preventing the formation of hydrogen sulfide while still enhancing biological nutrient reduction in anoxic conditions.


Hope you enjoyed,
Aviad

 

 

Can't say how much of this factual and how much is conjecture since there are no scientific sources cited, but interesting none-the-less.

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