These a few posts of mine from a thread on the advanced topics forum entitled: "Dosing nitrate to reduce phospahte" ; fyi and discussion:
Interesting thread . Most have done a good job getting past some of the nonsense and irritation and name calling and stayed on point.
A few comments to consider:
It's certainly seems counter intuitive to dose nitrate or another nitrogen source but it may make sense.
The redfeild ratio is rather useless as a guide other than to offer perspective on the general en masse proportions of carbon(C)106:N) 16: 1 P in ocean plankton. Organisms may approximate those levels but some including some bacteria vary significantly . Even if food put in the tank is close to those proportions, the activity in the tank may not use them in those proportions. All in all, trying to use the redfield ratio to obtain a generalized optimal N to P ratio seems convoluted. Using tank levels of N and P vs natural seawater levels seems smarter and more direct.
To clarify the idea as to why dosing N might be necessary, a brief look at the three major nutrients coming in and going out of the bio available mix in the tank may be helpful
Organic carbon coming in for the most part with foods can be used for energy or sunk in refractory( non bio available) organics like humic and fulvic acids ;some may also be contributed by photosynthesis. So, the amount coming into the tank is not really the bio available amount in the tank.
In many tanks it seems there is a shortfall as N and P levels climb. If there was enough organic C, the bacteria would use up the N and P too and tank levels would approximate nsw levels ( PO4 ca .005ppm and NO3ca. 0.2ppm) more often than they do. This imbalance is the basis for organic carbon dosing( vinegar, vodka, pellets, sugar, etc)
Unfortunately, hobby level measurement of organic carbon is not possible. Even high level analyses with $ 50 K analyzers don't really tell you what organics are present and whether they are bio available. So, we use No3 and PO4 as sort of a surrogate measure for nutrients, often ignoring organic carbon.
The proportion of N in and N out varies vis a vie the proportion of P in and P out too. The bacteria , consume C,N and P for food( ie, they assimilate them) and in turn are exported primarily by skimming . Even if we assume they have a perfect 116C to16Nto1 P biomass and the food into the tank also has these exact proportions,more N will be exported than P.
Anaerobic activity where the bacteria use NO3 for oxygen when free oxygen is used up exports extra N . NO3 is reduced to N as the oxygen is taken ;some of the N which binds to other N forming N2 which bubbles out into the atmosphere. How much of this occurs is variable from tank to tank but it does deplete nitrogen in addition to the nitrogen assimilated by the bacteria as biomass;there is no other such exit for P .
This is why many use gfo or other adsorbents and or precipitants for PO4 along with organic carbon dosing.
Sometimes, N levels at 0 may induce some coral paleness, perhaps from an N deficiency for the zooxanthelae or the coral itself. Some think adding extra N via sodium nitrate or calcium nitrate will remedy that and also help the bacteria to reduce more P. Very plausible positions,imo. Some ,including me prefer to add extra N via aspartic acid and amino acid which also adds some organic carbon.
Herringfish,
I'm not sure it matters a whole lot which source of N you use but as requested this is is my thinking:
Potassium nitrate(KNO3) adds potassium I might not need or want. I would use it if I measured and needed more potassium.
Calcium nitrate(CaNO3) adds calcium which I'd rather add in normal doses balanced with carbonate alkalinity.
Sodium nitrate(NaNO3) adds sodium but I don't care about that as much as the calcium or potassium since there is so much sodium in the water(10,500ppm) any small addition won't affect ion ratios very much at all and will level out with water changes . I've tried it.
Aspartic acid contains nitrogen and organic carbon in the form of an essential acidic ammino acid that living things incuding corals use . I account for the carbon part by reducing the vodka dose to off set the extra carbon. I use L aspartic acid from I herb .com,an online health food vendor ,ca $6 for 250 grams.
It only takes 4 grams 2x per week for 650 gallons to get N where I want it 0.5 to 1ppm . I'm still observing it since I started it just 2 weeks ago. Sps coral color seems to have gotten richer and lps seem fuller but I may just be seeing what I want to see.
I've been dosing vodka and vinegar for organic carbon over 5 years with very good results. in keeping NO3 and PO4 low. Sugar even in small amounts caused coral browning and some recession. There is at least one study linking excess glucose to coral mortality. So, I don't use any sugar anymore.
Since it has virtually no water in it and 80 proof vodka is 60% water I discount the vokda by 2.5 ml for each gram of aspartate I dose. I I would discount 5% acetic acid vinegar by 8ml per gram of acetate dosed.I'm sure a more precise comparison of organic carbon content of each is possible but that's close enough for me . I use the same conversions for any solid organic carbon source, eg, sugar, vitamin C, etc.
I don't know that dosing nitrate in any form is necessary as a standard proceedure. If there is food in a tank or breathing fish some nitrogen( ammonia, nitrite or nitrate) is there. Again nsw levels are around 0.2 for nitrate and .005 pmm for PO4 at the surface. I think it's still experimental and I'm just tweaking things a bit for now. I like to get just a tinge of pink viewed from the side of the salifert NO3 test.
Interesting thread . Most have done a good job getting past some of the nonsense and irritation and name calling and stayed on point.
A few comments to consider:
It's certainly seems counter intuitive to dose nitrate or another nitrogen source but it may make sense.
The redfeild ratio is rather useless as a guide other than to offer perspective on the general en masse proportions of carbon(C)106:N) 16: 1 P in ocean plankton. Organisms may approximate those levels but some including some bacteria vary significantly . Even if food put in the tank is close to those proportions, the activity in the tank may not use them in those proportions. All in all, trying to use the redfield ratio to obtain a generalized optimal N to P ratio seems convoluted. Using tank levels of N and P vs natural seawater levels seems smarter and more direct.
To clarify the idea as to why dosing N might be necessary, a brief look at the three major nutrients coming in and going out of the bio available mix in the tank may be helpful
Organic carbon coming in for the most part with foods can be used for energy or sunk in refractory( non bio available) organics like humic and fulvic acids ;some may also be contributed by photosynthesis. So, the amount coming into the tank is not really the bio available amount in the tank.
In many tanks it seems there is a shortfall as N and P levels climb. If there was enough organic C, the bacteria would use up the N and P too and tank levels would approximate nsw levels ( PO4 ca .005ppm and NO3ca. 0.2ppm) more often than they do. This imbalance is the basis for organic carbon dosing( vinegar, vodka, pellets, sugar, etc)
Unfortunately, hobby level measurement of organic carbon is not possible. Even high level analyses with $ 50 K analyzers don't really tell you what organics are present and whether they are bio available. So, we use No3 and PO4 as sort of a surrogate measure for nutrients, often ignoring organic carbon.
The proportion of N in and N out varies vis a vie the proportion of P in and P out too. The bacteria , consume C,N and P for food( ie, they assimilate them) and in turn are exported primarily by skimming . Even if we assume they have a perfect 116C to16Nto1 P biomass and the food into the tank also has these exact proportions,more N will be exported than P.
Anaerobic activity where the bacteria use NO3 for oxygen when free oxygen is used up exports extra N . NO3 is reduced to N as the oxygen is taken ;some of the N which binds to other N forming N2 which bubbles out into the atmosphere. How much of this occurs is variable from tank to tank but it does deplete nitrogen in addition to the nitrogen assimilated by the bacteria as biomass;there is no other such exit for P .
This is why many use gfo or other adsorbents and or precipitants for PO4 along with organic carbon dosing.
Sometimes, N levels at 0 may induce some coral paleness, perhaps from an N deficiency for the zooxanthelae or the coral itself. Some think adding extra N via sodium nitrate or calcium nitrate will remedy that and also help the bacteria to reduce more P. Very plausible positions,imo. Some ,including me prefer to add extra N via aspartic acid and amino acid which also adds some organic carbon.
Herringfish,
I'm not sure it matters a whole lot which source of N you use but as requested this is is my thinking:
Potassium nitrate(KNO3) adds potassium I might not need or want. I would use it if I measured and needed more potassium.
Calcium nitrate(CaNO3) adds calcium which I'd rather add in normal doses balanced with carbonate alkalinity.
Sodium nitrate(NaNO3) adds sodium but I don't care about that as much as the calcium or potassium since there is so much sodium in the water(10,500ppm) any small addition won't affect ion ratios very much at all and will level out with water changes . I've tried it.
Aspartic acid contains nitrogen and organic carbon in the form of an essential acidic ammino acid that living things incuding corals use . I account for the carbon part by reducing the vodka dose to off set the extra carbon. I use L aspartic acid from I herb .com,an online health food vendor ,ca $6 for 250 grams.
It only takes 4 grams 2x per week for 650 gallons to get N where I want it 0.5 to 1ppm . I'm still observing it since I started it just 2 weeks ago. Sps coral color seems to have gotten richer and lps seem fuller but I may just be seeing what I want to see.
I've been dosing vodka and vinegar for organic carbon over 5 years with very good results. in keeping NO3 and PO4 low. Sugar even in small amounts caused coral browning and some recession. There is at least one study linking excess glucose to coral mortality. So, I don't use any sugar anymore.
Since it has virtually no water in it and 80 proof vodka is 60% water I discount the vokda by 2.5 ml for each gram of aspartate I dose. I I would discount 5% acetic acid vinegar by 8ml per gram of acetate dosed.I'm sure a more precise comparison of organic carbon content of each is possible but that's close enough for me . I use the same conversions for any solid organic carbon source, eg, sugar, vitamin C, etc.
I don't know that dosing nitrate in any form is necessary as a standard proceedure. If there is food in a tank or breathing fish some nitrogen( ammonia, nitrite or nitrate) is there. Again nsw levels are around 0.2 for nitrate and .005 pmm for PO4 at the surface. I think it's still experimental and I'm just tweaking things a bit for now. I like to get just a tinge of pink viewed from the side of the salifert NO3 test.