It has occurred to me that there is a lot of interest in how the fishless cycle work's and it's benefits of doing one. Whilst the fishless cycle is by no means, the be all, and end all, it is worth remembering that it is the most ethical and humane way of introducing fish, into your new aquarium.
Why? When fish are introduced into a new aquarium the nitrogen cycle starts to take place, that nice new filter has a job to do to keep your fish alive however before it can begin to do so, it has to have the required bacteria that will happily dispose of the fish waste produced by your new fishy friends, Ammonia (fish waste etc) turns into slightly less harmful Nitrites (still dangerous to have) into Nitrates the end product of the nitrifying bacteria which are common in almost all aquariums and certainly can be found in your normal tap water, whilst less toxic a reading above 40 would be cause for concern aiming for nitrates below 20ppm is acceptable there are still ongoing disputes about this.
How does it work? Basically what it does is artificially replace the ammonia produced by fish waste thus keeping your fish safe from ammonia poisoning and respiratory problems which could lead to the death of your fish prematurely in an un-cycled tank, and because we are able to control the amount of ammonia added (unlike fish food or indeed the use of hardy fish) the cycle will in most cases be a lot quicker and you will have the satisfaction of knowing it will be safe when you add your fish.
What do I need? The first thing you will need to arm yourself with is a good liquid testing kit, a bottle of household 100% pure ammonia (this must be free of perfumes and added colouring etc) commonly found in the UK at hardware shops such as B&Q. and a medicine syringe handy for the small ml's you may need.
got those? excellent.....
What next? What has worked for me and countless others is to turn the heater up to the low 80's this helps the growth of the nitrifying bacteria providing you have good circulation and extra air as oxygen levels deplete at high temps all should be well, it may be worth removing the carbon if any you have at this stage personally I only use it to remove meds from the water column as and when required. Test your tap water, that will get you into the swing of taking tests and give an estimation of what your tank water is likely to be. Note water that has a low ph, kh and gh will need to take extra steps to follow the cycle through.
Next you will need to work out how much ammonia to add to your tank, remember to subtract the displacement caused by substrates and decor that you have. By keeping to a basic required 4ppm not only will it be easier to read on those test cards it will be easier to half when the nitrifying bacteria starts to take hold, 2ppm is still plenty to fully stock a tank at the end of the fishless cycle. Build up the ammonia slowly over 2-3 days then when you have reached 4ppm simply wait until it starts to fall. When this has occurred simply top up the difference to read 4ppm again until the nitrites show a reading of 2.0 or above, at this stage knock down the ammonia you are adding to half the original dose so instead of adding to 4ppm add only to 2ppm, this will help speed the cycle along and will still be more than enough to fully stock the tank. (some will drop it in half again but I keep in mind that you may be stocking big fish that produce a lot of waste and although any unused bacteria will die back it is still viewed better than not having enough to cope with the bio load imposed upon it.) by this time the ammonia would have been consumed within 24hrs or less and the nitrates would have started to show, then simply keep adding until both ammonia and nitrites are zero a large water change of 50% will then be needed to help rid any high nitrates and you can fully stock your tank. remember to turn down the temp to suit the fish you are about to stock.
You may notice that your ph will fluctuate during your cycle and is not uncommon, the only time to intervene is when you have a ph falling to below 6 as this will stall your cycle but adding a coral bag or bicarbonate of soda will be enough to kick start it again, one teaspoon to 50ltrs water.
Can I cheat? Yes you can, if you have an existing tank with mature media placing some into your new filter or squeezing the media into the water column will help kick-start the process and the cycle is more than likely to be finished in some cases in less as 10 days.