UV in the freshwater aquarium

[dpatte]

I am curious who is using UV sterilization on their freshwater tanks.

Some questions that come to mind are:
- does a UV system destroy beneficial nitrification bacteria? If so, should it be avoided all together?
- is it better to put a uv within the input stream of a canister filter, or within the output stream, or perhaps on its own pump?
- does the water flow speed affect the actual UV efficacy, and is it better to run water slowly through a UV (to get better sterilization), or quickly (to get more water sterilized)?

I have turbotwist 3x and 9x units, and have generally added turbotwists to the output stream of MAGNUM 350 canisters running micron filters. Magnums have an average flow rate - ~350 GPH.  The magnums are not the primary mechanical filters in my tanks, but may perhaps be the primary biological filters on my tanks. But if the micron filter cuts out most particles (including bacteria) down to micron size, is there any bacteria left coming out of the filter to sterilize, or am I just wasting electricity?

Thanks.

[exv152]

UV does not destroy beneficial bacteria because it only pumps water from the column through the light, while the beneficial bacteria adhere to surfaces in your tank and filter. I used a uv filter on a discus tank before and found it to be good for that species of fish considering how sensitive it is to pathogens and other organisms, and it had its own pump.