What does having a "cycled" tank mean?

[bettaamatuer]

ive been a member for a few months and have seen people say their tanks are "cycled." What does this mean any explanations would be greatly appreciated im sorta embarassed i dont know what having a tank "cycled" means

[Rachel]

Oh don't be embarrassed, this is a great question and probably one many new betta keepers may have.

Nitrogen Cycle
When someone is talking about "cycling a tank" or having a "cycled tank" it is referring to the NITROGEN CYCLE. It is a naturally occurring process in which nitrifying bacteria makes chemical conversions in your aquarium. This bacteria is mainly produced and lives in your aquarium's filter. It may sound confusing at first, but the process is very simple. While you're attempting to "cycle" a tank, there are 4 things you want to test for: pH, ammonia, nitrite and nitrate.

The Nitrogen cycle goes from AMMONIA (produced by fish waste, the addition of pure ammonia yourself, etc.) and is converted to NITRITE and finally to NITRATE (Ammonia>Nitrite>Nitrate). So basically you will first detect an ammonia reading, then a bit later you will detect nitrite when you test the water, and finally you will start to see a nitrate reading. The first two stages of the nitrogen cycle can be harmful to fish (ammonia and nitrite). You are trying to achieve only a NITRATE reading. Nitrate is safe for fish to a certain level, and is easily controlled through partial water changes, live plants use some of it to grow, etc. So when a tank is successfully cycled the readings should be: Ammonia=0, Nitrite=0, Nitrate=some level.

The bacteria involved in the process:
Ammonia to Nitrite (controlled by nitrosomonas bacteria)
Nitrite to Nitrate (recently determined to be nitrospira bacteria. It was previously thought to be nitrobacter bacteria.)

Uncycled tanks
When you do full or partial water changes in a small, uncycled tank you never allow the natural Nitrogen Cycle process to occur because you should change the water before ammonia is detected. Therefore the bacteria is never formed to continue onto the next steps.

Fishless cycle
It is always better to do a "fishless cycle" (where you add the ammonia yourself and complete the cycle before adding any fish to the tank) if you have the option so that the fish are not stressed out by the chemical changes that will occur. As mentioned above, ammonia and nitrite are harmful to fish and bettas in particular can be sensitive to them.

Seeding the tank
There is also a way to "seed" a tank. This is using a method to speed the cycling process along. A few methods that can be used are: adding pure ammonia, placing gravel or a piece of filter medium from a tank that is already "cycled" inside the tank/filter, or using a product such as BioSpira made by MarineLand.

More information
We don't have a good article about the Nitrogen Cycle on the HB website yet, so for now I'll direct you to amanichen's website to read more about it: s94779296.onlinehome.us/website/Fish/articles/nitrogencycle.htm