What is Cycling a Tank?
When you put water in a tank it is clean, minus whatever may have been in your tap water. A fish tank is like a little ecosystem and it needs a set of beneficial microbes that have many functions, so too clean is not a good thing. One important function of these microbes is to metabolize fish waste (ammonia) into nitrites, and then further metabolize nitrites into nitrates.
Ammonia is highly toxic and easy to spot in your system. If you have ever cleaned with ammonia, you'll know it becomes a white cloud in water. This is the main reason a tank will fog up on you. Unfortunately, if the tank does fog due to ammonia it means it is likely at lethal levels (as little as 2ppm), so we'll try to avoid this by taking it slow and giving the bacteria time to grow, which will prevent ammonia from building in your tank.
Nitrites are also pretty toxic (as little as 1mg/L), but a second set of bacteria will start to grow as soon as nitrites show up and just like ammonia, nitrites don't have to get to toxic levels if only a couple fish are in the tank during the cycle.
I can't stress enough how easy this process will be if you just don't overload the tank.
The final waste product, and the least toxic, is nitrates (safe up to 40ppm). Right now the only way to remove nitrates is by doing partial water changes on your tank monthly: between 40% and 25% depending on fish load.
What we call the cycle is the process of growing enough bacteria in a tank to break down all toxic wastes into less-toxic nitrates. During this time there will be a spike in ammonia followed by a spike in nitrates until the bacteria reaches a population that breaks it down as soon as its produced.
There is a catch though, the bacteria needs ammonia to grow.
Therefore, letting a tank sit with water and no fish will not cycle it. Some people have added pure ammonia to the tank, and this may work, but I don't recommend it. I prefer a natural approach, and I have not lost a fish in a cycle ever. By being patient and not adding too many fish, or adding fish too soon, I'm confident you won't either.
As long as you take it slow and don't overload the tank.
In very rare cases I have helped people with tanks who didn't grow bacteria, even after 2 to 3 weeks. I suspect this was from using very pure water and having a very clean tank and filter. You can purchase bacteria to jump start the cycle, but despite the claims by the manufacturer it would still be a good idea to give it a couple weeks before filling the tank to full capacity with fish. I have also used old filters from an established tank to "seed" my new filter. The only downside to this is you can't be sure which bacterial strains you're introducing. When you purchase bacteria, you can be certain you are introducing all the appropriate strains for optimal filtration.
This whole process we have been discussing is referred to as biological filtration. That's because biological organisms are working to help "filter" out the toxic wastes into less-toxic wastes. Other types of filtration you may encounter are mechanical and chemical, but that will be discussed in another post.
Ammonia is highly toxic and easy to spot in your system. If you have ever cleaned with ammonia, you'll know it becomes a white cloud in water. This is the main reason a tank will fog up on you. Unfortunately, if the tank does fog due to ammonia it means it is likely at lethal levels (as little as 2ppm), so we'll try to avoid this by taking it slow and giving the bacteria time to grow, which will prevent ammonia from building in your tank.
Nitrites are also pretty toxic (as little as 1mg/L), but a second set of bacteria will start to grow as soon as nitrites show up and just like ammonia, nitrites don't have to get to toxic levels if only a couple fish are in the tank during the cycle.
I can't stress enough how easy this process will be if you just don't overload the tank.
The final waste product, and the least toxic, is nitrates (safe up to 40ppm). Right now the only way to remove nitrates is by doing partial water changes on your tank monthly: between 40% and 25% depending on fish load.
What we call the cycle is the process of growing enough bacteria in a tank to break down all toxic wastes into less-toxic nitrates. During this time there will be a spike in ammonia followed by a spike in nitrates until the bacteria reaches a population that breaks it down as soon as its produced.
There is a catch though, the bacteria needs ammonia to grow.
Therefore, letting a tank sit with water and no fish will not cycle it. Some people have added pure ammonia to the tank, and this may work, but I don't recommend it. I prefer a natural approach, and I have not lost a fish in a cycle ever. By being patient and not adding too many fish, or adding fish too soon, I'm confident you won't either.
As long as you take it slow and don't overload the tank.
In very rare cases I have helped people with tanks who didn't grow bacteria, even after 2 to 3 weeks. I suspect this was from using very pure water and having a very clean tank and filter. You can purchase bacteria to jump start the cycle, but despite the claims by the manufacturer it would still be a good idea to give it a couple weeks before filling the tank to full capacity with fish. I have also used old filters from an established tank to "seed" my new filter. The only downside to this is you can't be sure which bacterial strains you're introducing. When you purchase bacteria, you can be certain you are introducing all the appropriate strains for optimal filtration.
This whole process we have been discussing is referred to as biological filtration. That's because biological organisms are working to help "filter" out the toxic wastes into less-toxic wastes. Other types of filtration you may encounter are mechanical and chemical, but that will be discussed in another post.
