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Introduction
In the Nitrogen Cycle, the final step is the removal of nitrate by its conversion into nitrogen gas. The first two steps of the cycle, the conversion of ammonia to nitrite and the subsequent conversion of nitrite to nitrate, are carried out under aerobic conditions by specific bacteria in the filter. Introducing air into the water will enhance these changes.
However, the conversion of nitrate to nitrogen can only take place under anaerobic conditions and many people question whether these anaerobic conditions can exist in ponds and aquariums. The answer is these anaerobic conditions can and do occur.
What are Bio-films
Bio-films are made up of micro-organisms surrounded by the slime they secrete that are attached to both inert and living surfaces when the surfaces are in contact with water. Well known examples of bio-films are plaque on teeth, the slimy films that build up on the inside surfaces of flower vases and the slippery surfaces on pebbles in river water.
These very thin layers of water/slime/microbes adhere to surfaces in ponds and aquariums. These surfaces include pipe-work, pond liners, glass, filter parts and even live fish. The films can build up to between, say, 50 microns to 150 microns in thickness. When water passes by, they remain fixed and static although the speed of the water flow becomes a limiting factor to the bio-film thickness. Close to the surface, the films become anaerobic and it is in these layers that the anaerobic microbes in our Viresco™ products take up residence. This is where the nitrate in the water is reduced to nitrogen. This process is called denitrification. (One micron is 1000th of a millimetre)
In July 2000 a customer in Kent began to use Viresco™ Koi in his koi pond which has a glass viewing plate 7ft 6in by 4ft 2in. Prior to using Viresco™ Koi, he had to wipe down the inside of this glass plate nearly every day to clear it of algae bloom build- up. The day after introducing the Viresco™ into his pond, there was no algae build-up on the glass. Five days after introducing the product, he reported that he still had not wiped down the plate. A week later, it was still the same situation. He now is a regular user of Viresco™ Koi and no longer has algae bloom build-up on the inside of his glass viewing plate.
We understand that the bacteria in our product had, in the bio-film on the glass, preferenially displaced the algae that was adhering there. There was no way that the algae bloom could have been removed through nitrate starvation in, say, 12 hours. Nitrate could not have been taken down to zero in that time by the microbes in our Viresco™ .
In 2002, the editor of “Tropical Fish” magazine, Simon Wolstencroft, carried out a trial of our Viresco™ Aquarium product in his own aquarium. In the magazine he later wrote:
”Within ten days of adding the product, this level (nitrate) was halved. Within a month the levels were unmeasurable, even on a good quality test kit and have remained so. Furthermore, in almost three months of continuous use, the front glass of the aquarium has not needed to be cleaned of algae, and there has been a considerable reduction in sludge.”
Again, he is stating that no algae was present on the glass in all the time the trial was being conducted, ie well before the nitrate had dropped to zero. The bacteria in our product had displaced the algae bloom adhering to the bio-film on the surface of the glass.
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