As you know, the health of the animals that live in your custom aquarium or fish tank relies on proper and consistent aquarium maintenance. So far we’ve reviewed mechanical filtration, and we’ve reviewed chemical filtration. Now it’s time to take a look at the third crucial piece of the puzzle: biological filtration.
Biological filtration is the most important function of an aquarium filter. Biological filtration is facilitated in a filter with a coarse medium, usually a ceramic noodle or plastic, spiked ball called a “bio-ball”. The object of this medium is to grow bacteria. That’s right, some bacteria are actually good! The bacteria actually grow on all surfaces in the aquarium. The biological filter media simply creates a larger amount of surface area for the bacteria to grow on. Your gravel bed is also a great biological filter. These bacteria eat organic waste (fish urine, feces and leftover food) in your aquarium.
The Nitrogen Cycle
More specifically, bacteria in your fish tank facilitates the nitrogen cycle. The nitrogen cycle is the process by which organic matter is converted to gas and released from the water. In the first stage of the nitrogen cycle the bacteria begin to eat the organic waste and convert it into ammonia (NH3). Ammonia lowers the pH of your aquarium and also burns the fishes’ skin and gills making it difficult for them to breathe. It is also introduced directly into the aquarium in the form of urine by your fish.
Next, the bacteria begin to convert the ammonia into nitrite (NO2-). Nitrite is also highly toxic to fish, and both ammonia and nitrate levels should be monitored on a routine basis in order to ensure proper filter functionality. Both compounds are measured in ppm (parts per million) and both should always read zero (0) ppm in a properly maintained aquarium.
The third stage of the nitrogen cycle consists of the bacteria converting the nitrite into nitrate (NO3-). This compound is relatively non-toxic to fish as long as it does not reach excessive levels. Also measured in ppm, nitrates should be kept under 100-150 ppm in a freshwater or marine “fish-only” (no corals or live plants) aquarium and under 10 ppm in a marine reef aquarium. This is not the final stage of the nitrogen cycle but, in an aquarium, it is where nature stops (or slows drastically) and the hobbyist must pick up the slack.
Too much weird science for you? Give Diamond Aquatics a call and we’d be happy to help you maintain your aquarium, or answer any questions you may have.