The Cycle Explained
If you have inquired about freshwater aquariums, is
likely that you have stumbled upon the nitrogen cycle. The driving
biological force within freshwater tanks is the nitrogen cycle. Knowing
it is more important than you may think – it can make or break your tank
and determine the survival of your fish.

The Process
- First, you have fish.
When fish are added, they consume food. Some food will not be eaten,
and will begin to decompose along with plant wastes. Food eaten by the
fish is discarded into the tank water as well. Fish respiration also
contributes to waste product.
- Fish, plant, and food waste decomposes into ammonia. Ammonia is toxic to fish in high concentrations.
- Bacteria present in the tank breaks ammonia down into nitrites. Nitrites are still very toxic to fish.
- Nitrites are broken down into nitrates by bacteria called nitrobacter. Nitrates
are much less harmful to fish than ammonia or nitrites, but they are
still toxic in significant amounts and can cause algae blooms.
- Partial water changes will remove some nitrates from your aquarium. Live aquarium plants absorb nitrates as well.
Stay tuned next week for:
The Nitrogen Cycle Part 2: Establishing the Cycle in Your Tank

Photo Credit: Ilmari Karonen