How to cycle a tank

Cycling process

This is the single most important thing you have to do BEFORE getting the fish. You can get everything else – decor, substrate, plants, filter, heater – but you absolutely need to “cycle” the tank before adding fish. Days of fish-in-cycling are long gone now and it is considered cruel. Any fish which have to withstand ammonia/nitrite poisoning will have its lifespan and overall health affected and might even die. Luckily, we can do the fishless cycle which focuses on sustaining a colony of bacteria capable of processing ammonia and nitrites.

Cycling means to start a nitrogen cycle. The beneficial bacteria will populate your filter slowly over time but in order for them to multiply they need warmth (heater), oxygen (filter) and food (ammonia). This you can provide either by providing liquid ammonia /link or adding fish food. I recommend ammonia over fish food as ammonia can be administered precisely while fish food is a bit of a lucky guess on how much to add. Make sure you buy ammonia with no additives.

Read, research, compare!

Do not impulse buy. That cute fish might look good in your tank at first but after it grows to 20cm, you might think twice. Some fish might be also aggressive with their own species or others. Sometimes it is impossible to prevent even if you made sure. Better be prepared to move the aggressor to a different tank, if you can´t do it, best not to risk.

Preparation:

1x household ammonia
1x syringe
1x API freshwater master kit
1x Seachem Prime (dechlorinator)
1x thermometer
1x filter
1x heater
ammonia calculator
10x lots of patience

For fishless cycle, we will be using ammonia. This is to keep the culture of bacteria which are slowly growing alive and fed. Once you get the fish, adding ammonia is not needed, as the good bacteria will transform it into nitrite and then nitrates. The amount needed to be added varies - if you want to stock straight away, like me, I was always aiming about 3-4ppm of ammonia. Add one injection in the evening, then test the following evening. If the amount of ammonia is still around 2ppm or it has not changed, skip adding that night and test again the following night until the ammonia gets to around 1ppm or less, then you can inject the difference to bring it up to your desired level. 

This will take some time, however, after a week or so, ammonia vial will become yellow (means 0 ammonia) and then you can start measuring for nitrites (vial for testing will be dark purple). This stage takes even longer than the first stage but this is where patience is required. Then, approximately after 2 weeks, nitrites will go down to 0 (vial will be blue). Your nitrates will start off yellow, then become orange and will be dark red in the last stage. This indicates your cycle has been completed and you can do a large water change. Water changes are NOT required while cycling, but watch your pH as it is possible for it to crash during this process.

Note: the vial colours on this site refer to using API Freshwater master kit