The Un-Filters 401 Chapter 4
Limitations of UV Sterilizers
Of course, the only algae cells that will be ‘sterilized’ are those free-floating single celled forms that pass through the housing and are directly exposed to the UVC. Attached algae, string algae and even free floating algae in areas that are relatively uncirculated will not be exposed and therefore will not be controlled.
Also, the presence of algae in the water is proof positive of an available supply of nitrates that the algae are consuming. If the algae in the water are “controlled”, it stands to reason that whatever amount of nitrate that the algae were consuming will remain unconsumed in the water. This can lead to a situation where the UV can actually mask very high levels of nitrate in the water. Those high levels might then lead to rampant string algae growth, as the algae that don’t pass through the UV benefits from less competition for the available nitrates.
On rare occasions UV’s can also mask a real water quality issue. The normal nitrogen cycle, ammonia to nitrite to nitrate, can stall when nitrate levels become saturated. High nitrates themselves are not particularly toxic to fish, but once the water has reached its carrying capacity for nitrates, well, that means no more nitrates can be converted from nitrites, and nitrite levels rise, and that’s a whole ‘nother story. Nitrites are toxic, and if they reach saturation then ammonia levels spike – but by that point the fish are already sushi.
So even when all is working perfectly, you need to deal with those nitrates! To avoid problems, UV systems should be used in concert with an aggressive Nitrate Removal System – the Bog. Consider running the water that you’re passing through the UV back through an Active Bog. The plants there will remove the nitrates that will otherwise fuel an explosion of string algae, and your pond will be truly sustainable, the biological cycle complete. See Filtration 401, Chapters 5 and 6 for more information on Active Bogs.
Of course, the only algae cells that will be ‘sterilized’ are those free-floating single celled forms that pass through the housing and are directly exposed to the UVC. Attached algae, string algae and even free floating algae in areas that are relatively uncirculated will not be exposed and therefore will not be controlled.
Also, the presence of algae in the water is proof positive of an available supply of nitrates that the algae are consuming. If the algae in the water are “controlled”, it stands to reason that whatever amount of nitrate that the algae were consuming will remain unconsumed in the water. This can lead to a situation where the UV can actually mask very high levels of nitrate in the water. Those high levels might then lead to rampant string algae growth, as the algae that don’t pass through the UV benefits from less competition for the available nitrates.
On rare occasions UV’s can also mask a real water quality issue. The normal nitrogen cycle, ammonia to nitrite to nitrate, can stall when nitrate levels become saturated. High nitrates themselves are not particularly toxic to fish, but once the water has reached its carrying capacity for nitrates, well, that means no more nitrates can be converted from nitrites, and nitrite levels rise, and that’s a whole ‘nother story. Nitrites are toxic, and if they reach saturation then ammonia levels spike – but by that point the fish are already sushi.
So even when all is working perfectly, you need to deal with those nitrates! To avoid problems, UV systems should be used in concert with an aggressive Nitrate Removal System – the Bog. Consider running the water that you’re passing through the UV back through an Active Bog. The plants there will remove the nitrates that will otherwise fuel an explosion of string algae, and your pond will be truly sustainable, the biological cycle complete. See Filtration 401, Chapters 5 and 6 for more information on Active Bogs.
