Every new fish tank goes through something called the nitrogen cycle. Let me try to explain. Fish produce waste in the form of a chemical called ammonia. This chemical is toxic to fish, but is food for a certain kind of bacteria. This bacteria is very beneficial and you definately want it in your tank. Fortunately, you don't have to go looking for it. If you have ammonia in your tank, eventually you will get this bacteria. O.k. so far? When this bacteria comes and eats the ammonia, it produces waste chemicals called nitrites (the second "i" is important for later.) These chemicals are toxic to fish, too. Hail another kind of bacteria. It, too, will appear in your tank with little help from you as long as you have a good supply of nitrites. When this second bacteria eats the nitrites, yes, you guessed it. It produces more chemical waste called nitrates (see the importance of the bold type now?). Nitrates are toxic to your fish only at high levels. Unfortunately, there are no bacteria to come and take care of the nitrates. You have to do weekly water changes of about 25% of the water in your tank to keep them at low enough levels. So how do you get your tank to grow this bacteria without putting your fish at risk? Fishless Cycling!!!
There are different ways to fishless cycle, but this is what has worked for me.
1. Go buy your tank and accessories. I highly encourage getting at least a 5 gallon tank for two reasons: the smaller the tank, the more maintenance required and the less fish you can have. You will also need an electric filter with a bio-wheel (a mechanism that looks like a paddle boat wheel for growing bacteria), a hood with a light, gravel, an aquarium thermometer, water conditioner (to remove chlorine and chloramine from your tap water), heater (if necessary), aquarium-safe decor, and aquarium-safe silk plants (you can add live plants later once you get the hang of things.) You will also need chemical test kits for ammonia, nitrite, and nitrate.
2. Set everything up. Rinse everything (except the electric part of the filter, of course) with tap water only. Do not use any kind of soap or detergent as the residue can hurt your fish. Put your gravel, decor, silk plants, heater, and thermometer in your tank. Follow the directions to set up your filter. Put your water in and treat it with the water conditioner. Get your filter running. Put your hood on and make sure your light works.
3. Add your ammonia source. I use regular, dye and perfume free household ammonia, 2 teaspoons per 10 gallons. Some people like to put something in the tank that will rot and cause ammonia, like dead shrimp. Whatever.
4. Add something from an established tank if you can. Your local fish store may be able to provide you with some gravel or something from their already cycled tanks. This will really make things progress a lot faster as it will contain the bacteria you are trying to grow.
5. Wait, wait, wait. After a few days, test for ammonia levels and nitrite levels. As the first set of bacteria grows, the ammonia levels will go down and the nitrite levels will go up. The first waiting period is for the ammonia levels to go to zero. If you have something from an established tank, this could take a few days to a couple of weeks. If you don't, it will take longer. Once the ammonia levels go to zero, start adding about a quarter to half of the original amount of ammonia to the tank. It should disappear overnight. If it doesn't, wait until the ammonia levels go back to zero, then add less until your ammonia levels return to zero overnight, every day. This means you have a good supply of the first bacteria. The next phase is waiting for the second kind of bacteria to grow. This is the longest phase and is characterized by really high nitrite readings for a really long time. Don't give up. Keep adding your ammonia. Eventually the nitrites will all of a sudden go to zero. This means your cycle is complete. Hold on, though. At the end of the cycle you will have really high nitrates. To lower them, do a massive water change without disturbing the gravel, decor, and filter in your tank. Remove as much of the water as you can. When you replace it, treat your water with the water conditioner before you put it in your tank. Chlorine and chloramine will kill your bacteria. Once you replace all your water, let the tank sit overnight then test for ammonia and nitrites one more time. If they are still zero, you're ready for fish! Note: My first tank cycling took 40 days. I did not have access to gravel from a cycled tank. My later tanks took a couple of weeks. I always added gravel and/or something else from my first tank.
6. Adding fish. Research, research, research what fish you want and the care they require while your tank is cycling. You do not want to overstock your tank or get baby fish that grow really big and put them in a small tank. Use the internet or go to the library. Aquaria Central is an online forum that I use. You can search the various topics for information or sign up and ask questions. Never buy a fish you know little or nothing about. This is one of the main reasons for tank problems and fish death. Also, it's best to add fish a few at a time until your tank is fully stocked. Keep up the general maintenance (see general maintenance section) and enjoy!
