When people talk about cycling tanks this is what they are referring to. This is a process that happens in both freshwater and saltwater aquariums alike. It’s important to cycle a tank before adding any livestock. To summarize it up – the cycle takes ammonia which is toxic and converts it to a safer product called nitrate.
The cycle starts with ammonia. Ammonia comes from several sources such as broken down fish food or fish excretion. Bacteria consumes ammonia and creates a byproduct called nitrite. Without bacteria present, ammonia levels would rise to toxic levels quickly and kill any living fish in the tank. Nitrite is considered less toxic than ammonia but it’s still unhealthy.
A different bacteria will consume the nitrite and produce a byproduct of nitrate. Nitrate is considered much less harmful than ammonia or nitrite. It even gets used by plants, algae and coral to grow. It can still be harmful in very high levels though. It can be reduced in a number or ways, which we’ll discuss later, but the most common way is through water changes. By taking out old water and replacing with new water we reduce these levels easily to safe ranges. There are also bacteria that can feed off of nitrate and turn it into nitrogen gas, which is then released from the water. This takes place is anaerobic areas of the tank where oxygen is very limited.