Filter Facts: Nitrifying Bacteria

By Rich Street

Pick up most any published book on basic fish keeping and you will see a diagram of the what is called the "Nitrogen Cycle." Ammonia produced by fish waste is oxidized into nitrite by Nitrosomonas bacteria and the nitrite is oxidized by Nitrobacter bacteria into nitrate, right? For over 30 years this cycle has been taken as fact. Enter the modern methods of molecular biology, including cloning, DNA sequencing, DNA finger printing, and others to prove this wrong.

Research has shown the bacteria responsible for ammonia oxidation are newly discovered members of the Nitrospira and Nitrosomonas genera and the bacteria responsible for nitrite oxidation belong to the phylum Nitrospira. The last one is the "Big Deal" to pay attention to as we start up the pond filters in Spring.

The big question for some is who cares which bacteria it is? Your pocket book might --- the research additionally suggests that the addition of "magic" filter starters that supposedly contain Nitrosomonas and Nitrobacter have little or no benefit in accelerating the start up of a new filter, as they do not contain the correct species of nitrifying bacteria. Marineland products, of course, cares because they cloned the new bacteria which does work and now sell it as "Bio-Spira." A 32oz. bottle treats just less than 1000 gallons, so even though it is the correct bacteria it could still be an expensive solution if you have a big pond.

If you shut your filter down last fall remember to clean it thoroughly before restarting it. Many folks start their filters in spring to give it the 2 to 3 months it is going to need to get on line. Watch the water chemistry, being ever ready to make water changes when the ammonia and then nitrite spike part way through the process. These spikes are normal to "new tank syndrome" and may be tempered by bacteria in an existing pond, but will usually still occur to some extent when the filter starts to process. Don’t ignore testing as ammonia and nitrite both are killers of fish.

This article is based on information presented by Dr. Tim Hovanec at the 2002 AKCA Seminar.

For more information you can search the web for the term "nitrospira" or go to these websites: