Vodka dosing in a saltwater aquarium

Vodka dosing in a reef tank

This sounds like a strange concept–and it is–but it works. Vodka dosing in a reef tank is a proven method to improve water quality by removing nitrates and phosphates from the water. Let me share some of the benefits of vodka dosing in a reef aquarium with you by answering some common questions:

What is vodka dosing in a reef tank?

Vodka dosing is a technique to reduce or even eliminate detectable levels of nitrate and phosphate from a reef tank.  The chemistry involved behind the scenes is actually not specific to vodka–it is ‘organic carbon’ dosing. In the case of vodka dosing, the aquarist has chosen ethanol (ethyl alcohol) as the organic carbon of choice–but other organic carbons could also be used. Technically, you could achieve the same results by using sugar–and some people do. I don’t recommend using something like maple syrup, which is extremely expensive and has other things in it besides plain sugar, but you certainly could use a sugar solution as a source of carbon if you prefer.

How does vodka dosing in a reef tank work?

When you dose vodka in your reef tank, you essentially feed helpful bacteria with the carbon calories that are in the vodka. By feeding those bacteria the carbon from the vodka, you are providing extra food which will cause their population to explode. Those helpful bacteria then later remove nitrates and phosphates from the water column. Pretty cool, eh? So you’re essentially boosting the biodiversity in your tank, which in turn causes the nitrates and phosphates to go down. Awesome stuff.

Why should I consider dosing vodka in my tank?

You should consider dosing vodka in your saltwater aquarium if you are an experienced saltwater aquarium hobbyist and despite proper, appropriate water changes, you consistently have elevated nitrates or phosphates in your tank. Quite frankly, that is probably the majority of advanced aquarists.

How much vodka is needed?

Remember, the goal with dosing vodka in a reef tank is to feed carbon to the good bacteria in the tank that will then, in turn, eat nitrates and phosphates. In that way, the process is a little bit like cycling your tank. When you cycle your tank, you’re feeding ammonia to bacteria to boost their growth, so that they can help filter your water once you add fish or corals. But if you recall, the advice given when starting out a new saltwater aquarium is to go slow.

You don’t want to overwhelm the bacteria in the biological filter–you need to allow time for the bacterial colony to catch up. That same principle is involved with dosing vodka. You want to start out with a small amount of vodka and increase it, over time, allowing the bacterial population to grow. The amount of vodka you start with is a really, really small amount. Really small. The recommended starting dose is 0.1mL per 25 gallons of net water volume per day for days 1-3, followed by 0.2mL per 25 gallons days 4-7, and then the addition of 0.5mL per week (regardless of aquarium volume), until nitrates become undetectable.

Please keep in mind that these guidelines were provided based on an assumed alcohol concentration of 40% (80 proof).

Vodka dosing in a saltwater aquarium

Vodka dosing: Step-by-step 

  • Step 1: Determine the size of your reef tank, in gallons (technically we are looking for the water volume here. I have a 92-gallon tank + a 20-gallon sump, but I also have a lot of live rock and sand. So I’m going to assume those volumes just about cancel out and therefore my total volume for this calculation is about 92 gallons.
  • Step 2: Pour yourself a drink.
  • Step 3: Measure out 0.1mL of vodka for every 25-gallons of tank volume. For my 92-gallon tank, I need 0.37 mL of Vodka
  • Step 4: Double-check your measurement to be sure you didn’t measure too much
  • Step 5: Scoop out a liter or two of tank water in a reef-safe container and add your vodka to it (diluting the vodka) and then slowly add it to your sump. You can use a dosing pump, start a siphon, or simply slowly pour it into the sump yourself.
  • Step 6: Repeat the same thing, once a day, for the next two days (three in total, including the first).
  • Step 7: About 8-12 hours later (try to pick the same length of time after dosing each day) measure your phosphate and nitrate levels and record them in your Reef Journal

On Days 4-7, double the amount of vodka used to 0.2mL per gallon of tank volume For each week after that, you want to add 0.5 mL vodka more…total…not per gallon. For example, in the calculations for my 92-gallon tank would be: 0.1mL per 25 gallons = 0.37mL for days 1-3, 0.74 mL for days 4-7, Days 8-14 would be 1.24 mL, Days 15-21 would be 1.74, Days 22-28 would be 2.24 mL and so on… You only keep increasing the vodka dose as long as the nitrates and phosphates are increasing or stable.

Once they start decreasing, you hold that dose steady until your nitrates and phosphates drop to zero, and then cut your vodka dose in half.

Equipment for vodka dosing

The amount of vodka that you will need to measure out is quite small. The best tool for this is a 1mL syringe. You can pick these up at Amazon for just a few dollars:

5 small 1 mL syringes with blue plungers
a 1mL syringe is perfect for measuring out small volumes like we need for vodka dosing

A dosing pump is quite useful at automating this otherwise manual daily task: You should definitely be running a protein skimmer, too–and expect to get more productive skimming as a result of the dosing. Find the best protein skimmer for your tank here. 

Warnings and precautions

Adding too much vodka to your tank can be catastrophic…as in…, you could kill everything. Be very careful when measuring, double-check before you add it to your tank. Remember, you’re doing this to try and get perfect, pristine water conditions–but it’s not worth hurting your livestock. If you see any signs of stress. Stop. If you miss a dose, that’s fine. You just missed a dose. Don’t try to make up for the miss by adding twice as much next time. That could be a big mistake. Watch this video to learn more about reducing nitrates and phosphates by dosing vodka in a reef tank:

Vodka Dosing, an easy way to dose organic carbon

Alternatives to vodka dosing

As mentioned earlier, the magic ingredient in vodka that is the reason we are doing it in the first place is organic carbon. If you want to lower the nitrates in your aquarium but don’t want to use carbon, you could use sugar or vinegar instead. Either will work, but each comes with a small caveat. Dosing sugar takes an additional step because you want to dissolve the sugar in water first. Vinegar is already a liquid, but it has a pH lowering effect. You won’t be using very much of it, but if you are dosing over a long period of time, just monitor and make sure you don’t see any decline in pH.

A few other fun facts about vodka

While you’re here, why not learn a few other fun facts about Vodka, to impress your friends or win trivia night.

Does vodka go bad?

No, vodka does not go bad, unless you’re looking at a very long time horizon. Vodka is 80 proof, which means it is 40% alcohol and 60% water–that is so much alcohol that it won’t even freeze at common freezer temperatures–and if left in the cabinet under your fish tank, it should stay fresh for several decades.

Does vodka have carbs or sugar in it? 

An ounce of vodka has zero carbs, zero sugar, so you can feed your tank without worrying about it growing a ‘beer belly’ or getting diabetes :).

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