At some point of keeping our aquariums we may have overheard someone from the reefing community talk about carbon dosing. They may say they're adding vinegar to their tank or even vodka. Yes, vodka! You may have reacted to yourself "Um, what??" and under breath say "Like... one shot for me... and one shot for my tank??" but not truly know what dosing it actually does. Liquid carbon dosing has been around for more a while, and many manufacturers have taken notice of it and offer products to fulfill supplementation. However, if you're like many of us hobbyists scratching their heads on the matter, we will try to breakdown what liquid carbon dosing is.

vodka as a liquid carbon source for the reef aquarium
Vodka or nah?

How it Works

Carbon dosing ties into the findings of Alfred Redfield, who discovered that the ratio of carbon to nitrogen to phosphorus was nearly identical throughout the seas of the world - 106:16:1 respectively. Through these findings, reefers' intentions of dosing liquid carbon is to replicate these ratios when there seems to be an imbalance between nitrates and phosphates in their tank. This type of dosing enhances beneficial bacteria activity allowing them to multiply which in turn reduces the nutrients (which would otherwise fuel nuisance algae), improving water quality.

redfield ratio graph of carbon : nitrogen : phosphorus ratios found in the oceans around the world
Alfred Redfield's findings from the early 1900's

The Benefits of Carbon Dosing

Dosing helps boost established bio filtration, stimulating bacteria to colonize and consume the excess nutrients, nitrate and phosphate along with the liquid carbon. This important function of bacteria in the aquarium is the natural nitrogen cycle and will keep the tank from experiencing "New Tank Syndrome". The improvement on bio filtration reducing excess nutrients also reduces nuisance algaes' favorite fuel.

An increase in beneficial bacteria population also means that your fish can be spoiled with some extra feedings as the bacteria are able to handle the heavier feeding which would otherwise add to the buildup of algal nutrition. Extra feeding is also known to have positive effects on coral growth and coloration. However, if extra feeding isn't your thing, the boost of bio filtration can mean that your aquarium can handle more fish, however, not all at once.... which would shock the system and allowing less time for the tank to find its balance - a great rookie mistake many of us make.

During the breakdown of organic particulates, liquid carbon dosing can form "marine/reef snow" in your aquarium, a natural coral food. Bacteria, in the process of converting waste through the nitrogen cycle, colonize organic particles. These particles can be flushed from rockwork by strong water movement, into the water column, to eventually be consumed by coral, clams, tube worms and other opportunistic filter feeders, with any excess skimmed out or removed through water changes.

Before getting Started

test kits to dial in where your nutrients are before considering using liquid carbon dosing
Test. Test. And test some more.

First thing needed are test kits. Make sure your tank can benefit from liquid carbon dosing by testing nitrate and phosphate to breakdown where the levels are at. If you have a high-nutrient system with levels out of acceptable reef parameters a water change alone won't correct, dosing carbon can be considered.

Have an efficient protein skimmer. Excess bacteria will make its way into the water column, becoming food for filter feeders, but should be skimmed out to keep the water quality from dwindling. The skimmer should be the primary extraction point.


As dosing liquid carbon gained ground among hobbyists, manufacturers have responded with a few carbon based supplements, each with their own dosage instructions based on nutrient levels. Here are just a few examples of suggested dosages for high-nutrient levels:

  • Brightwell Aquatics Reef BioFuel = 5 ml per 50 gallons daily
  • Tropic Marine NP Bacto-Balance = 3ml per 27 gallons daily
  • Red Sea NO3:PO4-X = Up to 1 ml per 25 gallons daily
  • All tanks have different parameters, so like many things in this hobby, changes to your tanks water chemistry should be done slowly. Many suggest even half the recommended dosage and dosing multiple times a day, so using an automatic dosing system may be needed. Note your nitrate and phosphate starting point before dosing and slowly reduce it to the desired level. When the desired level is reached, smaller doses can be made to keep levels maintained.

    If you prefer to use vodka or distilled vinegar, there is a noted ratio discrepancy between the two in the reef community of 1ml vodka to 7ml of distilled vinegar. Again, dose slowly with a starting dose of vodka at around .1ml per 25 gallons for the first half of the week. Note any negative effects, and if none, slowly increase the dosage each week until nutrient levels begin to drop.

    Low Nutrient Systems

    In response to ULNS (ultra low nutrient systems) there are supplements available to help promote the beneficial bacteria population that inhabit your live rock and substrate. Products like ATI Nutrition CNP help get out-of-balance nutrients, where either one is way out of the Redfield ratio, in order. Out-of-balance organic compounds and nutrients will slow growth, inhibit coloration, and can eventually kill coral. Supplementing nitrogen or phosphorus restore balance, while carbon helps promote the growth of bacteria that naturally consumes the excess.

    Final Thoughts

    Although liquid carbon dosing is meant to breakdown high nutrient levels and improve your water quality, it's possible that it can bottom out your nitrates and phosphates. With the lack of nitrate, phosphate and carbon nutrients, the beneficial bacteria colonies may dwindle allowing a potential outbreak of dinoflagellates, diatoms or even red slime bacteria. So, if you are considering dosing liquid carbon, we must emphasize that test kits and a good skimmer are key to success.