Cycling - The Nitrogen Cycle

There are various methods to get your tank ready for your Betta. Not everyone will agree with all methods, but I will explain all of them. Which ever you do, the temperature should be always be 78f/26c for your Betta.

N.B. It is the filter that cycles, not the tank.

MYTH- A filter will not cycle by leaving a fishless tank running for one, two, or even twenty weeks.
TRUTH- It will only start to cycle once a waste product is present.


Some people keep their Bettas in unfiltered tanks, but this means that a few rules must be followed to keep your Betta happy. Water changes must be carried out regularly to remove waste so that Ammonia doesn't build up. Ammonia is produced through fish waste and uneaten food, and is highly toxic to fish. The frequency of water changes will depend on the size of the tank, so having a good water test kit is very important. The APi liquid test kit is probably the best one to use. In tanks of less than 5 gallons, it may be necessary to carry out water changes every other day. You will need to check for ammonia daily, and once you have even a slight ammonia reading, its time to do the water change.

N.B. Remember that every time you add new water, you will need to use a dechlorinator to remove chlorine and heavy metals. APi StressCoat is commonly used. Also be sure to match the temperature of the new water with that of the tank water.

More frequent 50% water changes are less stressful to the betta than less frequent 80/90% water changes. However, all water changes can increase stress to your fish



Before explaining cycling a filter, it is a good idea to have a basic understanding of what the nitrogen cycle is, and how it is applicable to your fish tank.
This is just a very basic explanation of how a fully mature filter works.
When you have fish in your tank they will produce waste, which will break down to produce Ammonia. Uneaten foods will also produce Ammonia. The toxic Ammonia is broken down by bacteria in your filter to produce Nitrite (note the i), which is also toxic to fish. Another type of bacteria in your mature filter will then break down the nitrite into nitrate. Nitrate is only bad in high concentrations.
So, thats what happens in your filter -
Fish waste/food -> Ammonia -> Nitrite -> Nitrate.



Shooping list -
Pure Ammonia
Ammonia test kit
Nitrite test kit

Cycling your filter without fish is obviously the safest way to establish a mature filter, as there are no fish present that can be harmed by toxins. People used to use fish food as a means to cycle their filters, but this is a very slow process and doesn't grow such a big colony of good bacteria. More recently pure Ammonia is used. Pure Ammonia is available from most general hardware stores and occassionally local fish shops (lfs). A fishless cycle can take anywhere from 4 to 8 weeks.
Once you have your tank sited with gravel/sand in and filled with dechlorinated water, get your heater and filter turned on. Allow the temperature to settle at your desired level.
Once you start the fishless cycle, do not change any water. If you have water loss through evaporation this can be topped off with dechlorinated water.

Time to start adding the Ammonia to your tank. Add the Ammonia dropwise, until your ammonia test kit registers approx 5ppm (parts per million). I suggest that in a 10 gallon tank you start by adding 4 or 5 drops then test the water. Add further drops as necessary to reach 5ppm. Once you have done this the first time you'll know how many drops to add next time:)

Test the water for Ammonia every day until the ammonia has reduced to 1ppm or less. When at 1ppm add ammonia again to take it back up to 5ppm. Keep doing this until the ammonia is being processed from 5ppm to zero in 12 hours. This will normally be around 2 weeks, so maybe start testing the water every 12 hours at around this time.

Once the ammonia is being processed from 5 to zero ppm, the filter has grown a good supply of the ammonia converting bacteria and you can start testing for nitrite. You will find that the nitrite will be off the scale of your test kit, but dont worry:)

Keep adding the pure ammonia every day to a level of 2ppm ammonia. You should continue to do this until your nitrite reading is zero for at least 24 hours. Once the nitrite starts to drop, it will drop rapidly. This stage can take longer than the initial stage so dont panic. Unfortunately there is nothing you can do to speed it up:(

Congratulations, your filter is cycled. You can stop adding the ammonia and start adding your fish. Using this method allows you to add a full stock of fish straight away.
N.B. If you are not going to add fish straight away, keep adding the pure ammonia at 2ppm until the day before you get your fish. This is because your filter needs the ammonia for the bacteria to live.


It is very important that you do not kill off the bacteria in the filter. The bacteria are held in the filter media, beit filter sponges or wool. Your filter media should only need cleaning once every 4-6 weeks. To clean it, gently squeeze the media in a bucket of old tank water (i.e. water you have just removed from your tank), and pick off any larger bits of debris. Never wash the media in tap water as this will kill the bacteria and you will have to start all over again, which you wont be able to do with fish in.


Another method to mature a filter, is to add fully mature filter media to your new filter. Never remove more than about 30% of mature media from an established filter if that tank has a full stock of fish. Removing too much may cause that filter to crash. Once you have put the mature media into your new filter it is important to keep it fed. This can be done with pure ammonia or by adding a fish or two. Do not add too many fish in one go using this method, but allow a week between adding new stock.


Many people do not agree with this method, but it was the only method used some 15 years ago. The idea was to set your tank up and add a few hardier fish such as Danios to cycle the filter. This method exposes the fish to very high ammonia and nitrite levels. To reduce the exposure to the toxins, regular water changes need to be carried out. However, this will seriously increase the time taken to cycle the filter as you will be removing the ammonia needed to produce the good bacteria.


There are many products, which claim to either instantly or very quickly cycle your filter. Most of these products I can not comment on as I have not used them. However, the general concensus from people who have tried them, is that they dont work.
There is one exception that I have personal experience with, so I feel I am qualified to give you my opinion. The product I have used is "Stability" by SeaChem. I have used Stability to cycle a 40 gallon Marine tank, and 4 freshwater tanks. You basically add the required amount of the product every day for seven days. Fish can be added on the second day as long as you continue to use the product for the full seven days. I have heard people say that it does not work, but when questioned about their experience, it becomes apparent that they have not actually used it themselves and therefore are not qualified to give an opinion. When I first used it, I kept a record of test results for the first month. I found that the Ammonia and nitrite levels never showed, as the product supplies the good bacteria needed to process these toxins. If you ever choose to try it, I suggest you test the water every day to ensure that it is working for you.