If fish are properly quarantined, I see no use for a UV
sterilizer. I own 2, and haven't used either for the last 5-6 years. The notion that it kills all the beneficial bacteria, is false. It will kill any that might be in the water column and flow through the UV
, but the nitrifying bacteria colonize sufaces, they are in very low concentrations in the water column. The amount of nitrifying bacteria that would be killed from the water column is negligible and would not pose a threat to biological filtration if the sterilizer were used 24/7.