Vodka Dosing

I had wondered for a while about the efficiency of organic carbon dosing for the control of nutrients, so decided to try my hand at Vodka dosing.

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Why use vodka dosing to lower nitrates?

I have always had a very efficient means of nutrient export with the use of a refugium in my sump. But after years of relying on cheato everything changed.

A bit of a back story...

My preferred macro algae has always been Chaetomorpha because of its amazing ability to absorb both NO3 and PO4, keeping my nutrients at negligible levels. However, when it started losing it’s colour and disintegrating it was time to look at alternatives.

It took me a few weeks to recognise the demise of the Chaeto because I always grew it under a red/blue LED grow lamp, therefore did not see the lack of vibrant green. Within this period my nitrate shot up to 50ppm!

I had become so reliant of the Chaeto to perform that I also hadn’t tested NO3 for months.

Initially, my immediate go-to was Red Sea NOPOX. I had a 500ml bottle of the stuff in my fish cupboard bought a couple of years prior, so it made sense to use it.

The NOPOX was very efficient and brought the nitrate down from 50ppm to 18ppm by the time I had finished the bottle, which was very quick, in about the month.

Why I decided to use Vodka

I decided that this was the perfect opportunity to try carbon dosing and settled on Vodka as my carbon source.

I stumbled upon and their very in depth guide to dosing with 80 proof Vodka. After purchasing a bottle, I added the first dose to my tank.

It is well worth reading their full guide on vodka dosing prior to dosing:

Can vodka dosing go wrong?

I had been dosing for 120 days using the chart provided, but nitrates were still on 18ppm. I decided to increase the dosage till I started seeing some results. Eventually my nitrates began reducing and I achieved 0.2ppm.


I used Vodka very successfully for at least 7-8 months, however there are drawbacks, one of them was catastrophic.

I noticed that my tank became increasingly riddled with brown powdery algae on the glass and was constantly cleaning it away.

The skimmer, as expected, pulled more from the water column, and what it did pull was black and horrible. Instead of a weekly skimmer clean, it was cleaning the cup out every 3-4 days.

Cyanobacteria began to rear it’s ugly head, however because my tank is coral dense it could not get a purchase.

I knew that I had to closely monitor my nutrients and checked on both phosphate and nitrate far more regularly than I had done before (every three days), ensuring that they did not bottom out.

Unfortunately, this was not good enough.

Within a three day period the Vodka dosing consumed all nutrients, and I can only assume they hit zero. When I tested phosphate and nitrate they were 0.003ppm and 0.2ppm respectively, but I could see something was drastically wrong!

Vodka dosing caused my tank to crash!

Over a three week period I lost countless fragile sps corals, primarily smaller colonies which were on the way to becoming fully established. Of the corals I have left, they are generally well established and large (my green plating monti is 12″ x 12″), but they too suffered rapid tissue necrosis to varying degrees.


I believe I used vodka very carefully, ensuring at all times that it did not deplete the available nutrients.

One thing it has taught me is never to tempt fate. Don’t keep nitrates as low as possible when your corals will be just as happy and just as colourful with higher levels. Having a value of 5ppm gives more scope for correction and less potential to bottom out.

Vodka Dosing In A Saltwater Aquarium
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