Thursday, February 07, 2013

Fun with ammonia

You may have heard the comedic feminist epigram: "a woman needs a man like a fish needs a bicycle."

Well... fish may not need a bicycle, but they do need a cycle. The period, in the life of a new aquarium, during which the biological filter is established, growing enough nitrifying bacteria to convert the waste products from the fish (ammonia) into still-toxic nitrite, and then much safer nitrate. While this is happening, the tank is said to be cycling, a process that is complete when ammonia and nitrite levels fall to zero (or as close as makes no difference) because you have enough bacteria to eat it all, and nitrate levels gradually rise until the next partial water change.

You can cycle a tank with a small number of fish, which is how we started off the biological filter in the BiUbe, but this is stressful for those fish as they're subjected to higher levels of ammonia and nitrite than is best for them, so this time round I was hoping to do a "fishless cycle."

A fairly easy concept to grasp but more complicated in its execution, the fishless cycle basically involves introducing chemical ammonia into a tank for the bacteria to feed on (and starting the colony off with some bacteria from an existing tank if possible) and waiting until you've grown a colony large enough to handle the waste from your fish, at which point the fish can be introduced. In practice this is a bit of a juggling act because (a) you don't know how much ammonia your colony of fish is generating and (b) you have to guess that amount and then add it daily to keep the bacteria fed until the fish arrive. It's also important to do regular testing to monitor the colony's progress. Too much ammonia can kill off the bacteria and put you back to square one.

The first challenge was finding a source of pure ammonia. Or ammonium hydroxide I should more properly say. Most of the bleach available from supermarkets is contaminated with perfumes and surfactants to make it more acceptable as a cleaning agent. Any of that is not good for the inside of an aquarium. After a short search we eventually found a local shop (of the kind we usually refer to as "plastic man" because they sell a huge array of plastic tubs, buckets and bowls) with a stock of Kleen Off - pure ammonium hydroxide. Result!

It's never as easy as that though is it? The bottle had no indication of concentration, so to arrive at the required ammonia levels (4 or 5 ppm) in our 130-litre tank I had to do some experimenting. I'd found a handy guide to fishless cycling that talked about adding "a few drops at a time", testing, and repeating until the numbers came up, so armed with a jug containing 2 litres of treated water, my bottle of ammonia and my testing kit, I made a start. First with 3 drops, then 7, then another 10, 20, 50. Pretty soon I was up to 200 drops in my 2 litres and the test phial had barely shifted from the weakest colour (0.05 ppm) to the next blob (0.1ppm). Pretty soon the water was looking pretty syrupy with ammonia and I was approaching the point where I'd be adding the equivalent of half a bottle to the tank every day. That can't be right! (I thought). Slowly the reality dawned on me - the ammonia was bleaching the dye in the test kit.

I think we'll be cycling this new tank with some fish from the BiUbe!

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