The Needs of Nitrifying Bacteria
Not only is ammonia produced by bacterial mineralization, it is also pumped into the water by the fish excrement. Basically, fish are swimming in a pool of their own filth and it is this that poisons them, causing damaged tissue, especially of the gills and kidneys. Ammonia poisoning also lowers resistance to disease, making the fish more susceptible to death, which is why aquarium hobbyists and pond enthusiasts refer to fish that have been poisoned by high levels of ammonia as “New Tank Syndrome.”
Along with toxic levels of ammonia, high nitrite levels also pose a problem. Nitrite poisoning keeps red blood cells from taking in oxygen, converting the hemoglobin in red blood cells to methemoglobin, a form of hemoglobin that does not bind oxygen, heightening the possibility of tissue hypoxia.
Because of this risk, it is important for pond keepers to establish the nitrogen cycle quickly and with as little stress to the fish and aquatic life in their pond as possible. Nitrifying bacteria (Nitrosomonas and Nitrobacter, respectively) use inorganics for their energy source and oxidize toxic ammonia and nitrite. Nitrosomonas breaks down ammonia into nitrite while Nitrobacter converts nitrite into nitrate, which can then be used as a source of nutrition for surrounding plants. These nitrifying bacteria colonize on gravel and sand and emit a slimy secretion that helps them attach to those surfaces. Both bacteria rely on their abilities to “fix” CO2 to fulfill their requirement for carbon. Because most of their energy goes into “fixing” CO2, very little is left over for reproduction. But it’s okay, considering their efficiency; a single Nitrosomonas cell can covert about the same amount of ammonia that it takes 1 million standard pond bacteria (heterotrophic bacteria) to convert.
To ensure that nitrifying bacteria grow and do their job, take care of a few things so that they can take care of business.
- Make sure that your pond has micronutrients for nitrifying bacteria, most importantly, ATP (Adenosine Tri-Phosphate.) This nutrient provides energy for the nitrifying bacteria to carry out cellular functions. Phosphates are also needed, particularly because Nitrobacter cannot oxidize nitrite without it.
- It is also important to make sure that the temperature of your pond is conducive to the growth of nitrifying bacteria. A good temperature is 75 to 85 degrees Fahrenheit. Ten degrees colder and its growth rate is substantially cut in half. At 120 degrees Fahrenheit, nitrifying bacteria cannot live to convert another day.
- Nitrifying bacteria also need specific pH levels in order to thrive. pH must be slightly basic at 7.8 to 8.0 for Nitrosonomas and 7.3 to 7.5 for Nitrobacter. Bacterial growth is stunted the more acidic the water pH gets.
- Dissolved oxygen levels must exceed 80% saturation in order for maximum nitrification. If levels drop below 2 parts per million, nitrification will not occur.
In order for nitrifying bacteria to make the biggest impact in restoring a natural nitrogen cycle to your pond, make sure these few things are taken care of. This will make it easier for the bacteria to do its job to make sure you have the cleanest, clearest pond possible.
