Back in January, my fishtank had got out of balance in its water chemistry. The nitrate levels were way up, causing a huge explosion of green algae.

I was faced with some unpleasant choices. I could buy some very expensive filters to remove the nitrate. Having already bought some expensive live rock for this purpose and had it fail I wasn't keen on that.

Or I could do some massive water changes. This would be expensive as it is a marine tank and the cost of salt can be quite high.

I came across some articles on the internet that suggested that dissolved carbon in the water encourages the growth of bacteria which break down the NO3. The preferred format for this is ethanol in the form of vodka. So I went to the bottle-shop and asked for a bottle of their cheapest vodka with the very lame excuse that it's for the fish, honestly.

The balance in all of this is getting enough in to the water to feed the bacteria without poisoning the fish. On the basis of somebody else's very conservative recommendations, I went even more conservative starting at 0.1 ml per day, increasing it weekly until I started to record measurable reductions in the nitrate.

For months, nothing seemed to be happening. What should happen is that the green algae should start to die and decompose. The first sign of this is not so much that you see a reduction in the algae as an increase in the activity of the protein skimmer- a special filter that uses fine bubbles to remove protein and other organic matter from the water.It wasn't until I was putting about 3 ml of vodka each day that the protein skimmer started to get really active.

At 8 ml I finally started to notice that the NO3 was reducing and that the algae was declining also. I did a bit of a water change and cleaned out the tank.

Today the level is down to zero! Well it probably is closer to 10 ppm as the indicator strips I use are high range indicators that don't show much below 20 ppm.

So after 4 months of daily dosing my fish tank, I can finally claim a victory! I intend to monitor the water for a little while yet and gradually reduce the amount of vodka I am adding. I expect the tank to look much cleaner and the remaining algae to start to disappear.