Does a UVC clarifier harm useful bacteria?


I purchased a UVC water clarifier about a week ago. Will the unit destroy useful bacteria?

all bacteria dwelling in open water and thus being carried past the UV light will be killed. Therefore, filter bacteria are usually not affected since they settle in the filter material, in the bottom gravel or on other surfaces and do not get in contact with the UV light which would be fatal for them. Problems may only occur shortly after having added biostarters, as long as the included bacteria have not yet settled. Therefore the UV clarifier should remain off for a while during this phase.

Should I leave the clarifier on permanently or rather only for a few hours every day?

If you use a UV clarifier it should be permanently in operation.

Some general information about using UV clarifiers in freshwater aquariums:

  • UV clarifiers can be very useful for treating contagious infections (Ichthyophthirius!) without medications, which is a valuable option in case of (medication) sensitive fish.
  • The pheromone communication of the animals (and also plants!) is at least affected by UV clarifiers; however I have never heard of serious or even noticeable problems.
  • Using UV clarifiers for achieving very low pathogen conditions is common practice in saltwater aquariums.
  • In ponds, UV clarifers are often used against floating algae (green water). Important: The algae coagulated/killed this way must be removed from the water circuit, otherwise they will decompose and then unnecessarily pollute the water which in the end supports the growth of new algae, among others.


Best regards

sera GmbH

Dr. Bodo Schnell


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