alexander_ktn
New member
While there are numerous threads discussing the possibility of dosing nitrate to lower phosphate in carbon dosing scenarios I haven't seen it elaborated or recipes supplied.
I have been carbon dosing on and off in my systems for years and I have also added nitrogen in the form of ammonium chloride and potassium nitrate when nitrate in the tanks was zero and phosphate was still at a high level that wouldn't budge.
When to dose?
If you struggle getting phosphate down with carbon dosing and either GFO doesn't do the trick for you or you don't have a way to use a phosphate absorber. E.g. if your phosphate stays at 0.08 for weeks despite zero nitrate and despite upping the carbon dose.
Why dose a nitrogen source?
The bacteria we want to grow by dosing carbon need nitrogen, phosphorus, carbon and other elements in order to reproduce or grow. If one of these elements is only available in very low concentrations it will limit the bacteria (this is also the whole premise behind adding carbon in the first place).
Sometimes when dosing carbon, nitrogen (in the form of nitrate) is reduced to a point where it becomes limiting to the bacteria and thus the reduction of phosphate seemingly comes to a halt even with adding more and more organic carbon. If we now add nitrate, the limitation disappears and the process can continue.
What will adding nitrate do to my corals?
This is an interesting question because we are of course afraid of browned out corals. I have not had any problems with this issue, since the nitrate additions are comparatively low and temporary. In this regard there is also a relatively recent study (2011) that shows the nitrate uptake by Stylophora corals at different nutrient levels, for the people that are interested in such papers. http://jeb.biologists.org/content/214/16/2749.full.pdf+html
How to go about it
I usually use a stock solution that contains 100mg/ml of nitrate, so dosing 1ml per 200 liters of tank water will add 0.5 ppm nitrate to the tank.
I usually dose the 1ml/200l daily until I see the desired reduction in phosphate or the nitrate value approaches 1-2ppm. So far phosphate started to go down reliably within days after starting to add nitrate.
What are the dangers
1) You might feed problem algae, though I have never noticed an increase in algae growth - I guess the bacteria we culture are quite good at utilizing the nitrogen source before it gets to algae.
2) If you use potassium nitrate it will increase potassium in the tank. Potassium levels in our tanks are at 200-400 ppm, though, and for each 1 ppm of nitrate you add, you only increase potassium by 0.6 ppm - so in my opinion negligible.
3) Corals browning out - I never had that problem and as written above, if you don't overdo it, you should be fine. I'd be more concerned about the effects of phosphate on the corals.
4) If you add too much nitrate while carbon dosing you might get to a point where phosphate becomes limiting to the corals. This might especially be an issue if you do not feed your tank enough and can lead to STN and bleaching or other serious problems.
5) You might get a bacterial bloom, as always with carbon dosing.
Recipe
This recipe makes 1 liter of stock solution that contains 100 g/l of nitrate.
1 ml of this solution will add 1 mg/l of nitrate to 100 liters of tank water (0.5 mg/l per 200 liters)
Needed:
163 grams potassium nitrate (KNO3)
1 liter RO/DI water
Preparation:
Dissolve 163 grams of potassium nitrate (KNO3) in 0.8 liter of RO/DI or distilled water and fill up to 1 liter. (You can also just add the 163 grams of potassium nitrate to 1 liter of water, it will be a slight bit more diluted but the effect is minuscule.) Using warmer water helps with dissolving the KNO3, because it's an endothermic reaction and uses up heat.
You can also use calcium or sodium nitrate but need to be aware that they have other molar masses and may contain water when you make your calculations.
Cheers, Alex
I have been carbon dosing on and off in my systems for years and I have also added nitrogen in the form of ammonium chloride and potassium nitrate when nitrate in the tanks was zero and phosphate was still at a high level that wouldn't budge.
When to dose?
If you struggle getting phosphate down with carbon dosing and either GFO doesn't do the trick for you or you don't have a way to use a phosphate absorber. E.g. if your phosphate stays at 0.08 for weeks despite zero nitrate and despite upping the carbon dose.
Why dose a nitrogen source?
The bacteria we want to grow by dosing carbon need nitrogen, phosphorus, carbon and other elements in order to reproduce or grow. If one of these elements is only available in very low concentrations it will limit the bacteria (this is also the whole premise behind adding carbon in the first place).
Sometimes when dosing carbon, nitrogen (in the form of nitrate) is reduced to a point where it becomes limiting to the bacteria and thus the reduction of phosphate seemingly comes to a halt even with adding more and more organic carbon. If we now add nitrate, the limitation disappears and the process can continue.
What will adding nitrate do to my corals?
This is an interesting question because we are of course afraid of browned out corals. I have not had any problems with this issue, since the nitrate additions are comparatively low and temporary. In this regard there is also a relatively recent study (2011) that shows the nitrate uptake by Stylophora corals at different nutrient levels, for the people that are interested in such papers. http://jeb.biologists.org/content/214/16/2749.full.pdf+html
How to go about it
I usually use a stock solution that contains 100mg/ml of nitrate, so dosing 1ml per 200 liters of tank water will add 0.5 ppm nitrate to the tank.
I usually dose the 1ml/200l daily until I see the desired reduction in phosphate or the nitrate value approaches 1-2ppm. So far phosphate started to go down reliably within days after starting to add nitrate.
What are the dangers
1) You might feed problem algae, though I have never noticed an increase in algae growth - I guess the bacteria we culture are quite good at utilizing the nitrogen source before it gets to algae.
2) If you use potassium nitrate it will increase potassium in the tank. Potassium levels in our tanks are at 200-400 ppm, though, and for each 1 ppm of nitrate you add, you only increase potassium by 0.6 ppm - so in my opinion negligible.
3) Corals browning out - I never had that problem and as written above, if you don't overdo it, you should be fine. I'd be more concerned about the effects of phosphate on the corals.
4) If you add too much nitrate while carbon dosing you might get to a point where phosphate becomes limiting to the corals. This might especially be an issue if you do not feed your tank enough and can lead to STN and bleaching or other serious problems.
5) You might get a bacterial bloom, as always with carbon dosing.
Recipe
This recipe makes 1 liter of stock solution that contains 100 g/l of nitrate.
1 ml of this solution will add 1 mg/l of nitrate to 100 liters of tank water (0.5 mg/l per 200 liters)
Needed:
163 grams potassium nitrate (KNO3)
1 liter RO/DI water
Preparation:
Dissolve 163 grams of potassium nitrate (KNO3) in 0.8 liter of RO/DI or distilled water and fill up to 1 liter. (You can also just add the 163 grams of potassium nitrate to 1 liter of water, it will be a slight bit more diluted but the effect is minuscule.) Using warmer water helps with dissolving the KNO3, because it's an endothermic reaction and uses up heat.
You can also use calcium or sodium nitrate but need to be aware that they have other molar masses and may contain water when you make your calculations.
Cheers, Alex
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