Aquarium Basics, Page 2
The Nitrification Cycle
Fish produce ammonia. Uneaten food that is left to decay and other organic wastes also produce ammonia. This can very rapidly reach a toxic level in the fish tank. In a properly set up tank, that is regularly maintained, properly filtered, and not overcrowded, ammonia is seldom a problem. However, it is still vitally important that the aquarist is aware of the cycle and how it impacts the fish that live in the tank.
This process creates something that aquarists call "biological filtration" or "biofilter" for short. In a brand new tank setup, there is no biofilter. Even though the water is fresh and clean, if you were to put a bunch of fish in this new tank, they would begin to produce ammonia, and this water would turn deadly poisonous in a very short time without a biofilter. So, how do we get one? Can we buy one? Unfortunately, you can't easily buy one. There are products that claim to "jumpstart" or begin this cycle in your new tank, but really the only thing they do are provide some financial security for their manufacturers. No, the only things you need to have a biofilter are things you probably already have.
First, you need an ammonia source. Of course, fish are good ammonia sources, but many fish have been sacrificed to cycle tanks, and in our modern age, such reckless sacrifice is tantamount to animal abuse. The preferred ammonia source for most hobbyists can be found in ordinary household ammonia (unscented and without other ingredients). You may even have some already in your cleaning supplies. The second thing you need is the bacteria. Don't despair, they are all around you. Where? In the air! They are everywhere. All they need is a surface to colonize (the gravel, tank walls, and your filter media make excellent houses for them), oxygen (which comes from the air), and ammonia (which you will add, but we'll get to that shortly). The last thing you'll need is an ammonia (NH3/NH4) test kit and a nitrite (NO2) test kit. For the purposes of cycling, any kind will work, so get the cheapest ones you can find. With all of those ingredients in place, you're ready to set up your biofilter. Most of the work is already done. All you have to do now is add some ammonia.
Before proceeding, let me state one word of caution here: household ammonia is a chemical. Like all household chemicals, it can be dangerous if improperly handled. Never directly breathe the vapors from the ammonia. Children should always seek assistance from their parents when handling chemicals, young children should just let their parents handle the chemicals. Wear gloves, an apron or smock, and eye protection when handling chemicals. A face mask might also be used.
Ok, the business end of it: You will need to add some ammonia to the tank. Just drop a few drops at a time in the water, and use the test kit to determine when 4-5 mg/L (ppm) is reached. Now, record on a sheet of paper the date, time, amount of ammonia used, and test kit reading. In 24 hours, test the water with the test kit again. If the ammonia level is below 4 mg/L, add some more. You want to keep the ammonia level at 4-5 mg/L for the first few days. Record your information again, and repeat this procedure for 4 days. What you should be finding is that you should start to have to use more and more ammonia to bring the ammonia level back up to 4-5 mg/L. If you haven't had to add any more yet, don't worry, sometimes it takes a couple of days before you have to start adding it.
Once the ammonia level falls to 0 mg/L between your 24 hour tests, the first stage bacterial colony has been built. Keep adding the ammonia as you have been doing, and begin testing the nitrites with the nitrite test kit. You'll keep doing everything the same way as before. (You're still recording all your results, right?)
Finally, when the nitrites test at 0 mg/L between your 24 hour tests, the second stage bacterial colony has been built, and your tank is fully cycled! You're almost ready to add fish. Before adding your new fish, you should now perform a 50-75% water change. This removes any excess nitrates and other chemicals that were produced during the cycling process. Drain off half to three-fourths of the water in the tank, and refill it with fresh clean water. If you're adding fish right now, be sure to use dechlorinated water. If you're not adding fish today, make sure that you do add your fish within a few days, or your newly established biofilter can die off, meaning that the cycle might have to partially or completely start over.
The entire cycling process can be as short as one week, or as long as 6 weeks. It depends on environmental factors and availability of bacterial spores. One way to speed the process up is to use a filter or some gravel from an existing established tank. This transplants some of the bacteria from the old tank to the new one.
In the mean time, while waiting for your cycle to complete, read the remaining articles in our beginner section, so that you'll know everything you need to know to take the best possible care of your fish when you get them!
Text and graphics (C) 2002, Andrew Phillips. Please do not use without permission.
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