Carbon Dosing and Supplementing with Nitrate (Nitrogen)

  • #1
When I planned my Reef, I initially planned around a DSB/Refugium for nutrient export.

When I went to buy my sand and macro's, the LFS advised me about carbon dosing, although at the time, I was simply introduced to Red Sea's NO3O4-X, and later learnt the method is known as Carbon Dosing. I have also read about Vodka and Vodka/Sugar/Vinegar dosing.

So I started dosing, and low and behold, my nitrates fell to zero very quickly, however PO4 remains high at 0.64ppm. So I started researching (and posting some questions on another forum) to understand the relationship between all the elements.

The subject of the Refield Ratio was introduced to my vocab, whereby the ratio of Organic Carbons:Nitratehosphate is in the realms of 106:16:1, and from what I can gather, it means in order to accelerate uptake of nutrient by addition of organic carbon, you need 106ppm of organic carbon to reduce 16ppm of nitrate, and you need 106 ppm of Organic carbon and 16ppm nitrate to reduce 1ppm of phosphate.

On these ratios, it's easy to see that Carbon Dosing will very quickly reduce/eliminate nitrates, which then removes the ratio required to reduce phosphates.

Enter Nitrate dosing - more specifically, Seachem Nitrogen (used as Freshwater plant fertiliser), to increase the nitrate content.

This where the science kicks in, and my brain starts to hurt, as it seems counter intuitive to dose nitrates, and continue carbon dosing, but based on what I'm reading so far, it seems to work.

I haven't started dosing Nitrogen yet as I don't fully understand the concept, but to me it's a very interesting area of water chemistry.

So let the discussion(s) begin:
- Do you carbon dose? Be it Vodka, VSV or other (NOPOX)
- Are you trying nitrates to maintain the ratio?
- What techniques are working/what has failed?
- Pitfalls and experiences?
- etc etc

And a reminder - please keep it on topic, factual and respectful. I think this is a very interesting topic, and given it's relative infancy, there's a lot to learn, that may make Saltwater fishkeeping even easier and cheaper.


  • #2
I was getting into carbon dosing and then discovered biopellets. My nitrates are nil and my phosphates are in the .03 ppm range with hanna digital meter.

If I were to dose nitrate, how would one determine how much nitrate to dose?

  • Thread Starter
  • #3
If I were to dose nitrate, how would one determine how much nitrate to dose?
This is the bit that made my head hurt

And is also the reason I haven't started with it - I don't do things to my tanks (FW or SW) that I don't have a comfortable understanding of, especially when I have livestock.

I have read a 'guide' that suggests starting with 0.5mL per 100L to start, and slowly increase to around 1mL per 100L (over say 5-6 weeks) - but this was only a guide posted on a forum.

I am yet to see a 'calculated' approach to the nitrate dosing that makes sense to me yet. (a guide similar to the Ammonia dosing for cycling)

I'm hoping someone may have tried this method, and has found that targeting x ppm of NO3 seems to work.

The Redfield ratio is not an exact science, so stay tuned, as I get my head around it, I'll make my decision on whether to try it.

EDIT: The more I think about it, I think the difficulty is in trying to establish the organic carbon content.

By my maths, if I want want to reduce 0.6ppm of PO4 (to bring it to 0.04ppm), then, I want a NO3 concentration of (16*0.6) = 9.6ppm, and thus (106*0.6) or 63.6ppm of Organic Carbon.

How does one figure out the organic carbon content?
Or do I target 10ppm of NO3? and thus - I have a problem, my livestock (corals) may not like such a high NO3 concentration.

<told you it was an interesting topic >
  • #4
yeah, I try to keep things as simple as possible in my reef tank. Makes my brain do loops when I have to add something that I'm already trying to eliminate for the corals.
Stang Man
  • #5
As long as you do proper water changes then you should not worry. These type doses if not monitoired at 3-4 times per day can turn your tank to mush, be careful dosing these elements or you may loose the whole tank, this is for advanced aquarist and there is a lot to it ( chemistry wise) and with out the proper equipment to monitor the tank then don't go that route.
  • Thread Starter
  • #6
this is for advanced aquarist and there is a lot to it ( chemistry wise) and with out the proper equipment to monitor the tank then don't go that route.

Duly noted

I'm still reading a lot about the topic, if for no other reason than to learn about as an area of interest. Like I've said, until I understand it, I won't be doing it.

Things are going pretty well at the moment, and chasing a number for PO4 (i.e. to get it below 0.1) may do more harm than good in my circumstance.

It's a topic that struck me as very interesting, hence I thought I'd start the discussion

Out of curiosity - what sort of monitoring equipment are you referring to? Obviously you're talking more high tech than liquid test kits..........
Stang Man
  • #7
Either type of test kits are good, all I'm saying is to be very carefull with this type dosing if you choose to go that route.

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