I know that UV will kill stuff like bacteria etc...

But what does the UV do that would be bad?? I don't totally understand the possible negative effects of long term usage of a UV filter. I have had one installed for a few days now and it has done it's job and I am ready to unhook it and place it into another tank of mine.

Just looking for peoples knowledge and experience with UV effects good, bad, long term, and short term.

Thanks!

So am I safe to assume there are no harmful effects or very little experience to make a judgment call ?

There is no physical reason I know of why UV would affect any nutrients, other than chelated ones, which are the trace elements. And, all that would mean is that the chelated elements would become less immediately available to the plants, but ultimately the plants would still get those elements through their roots. As far as I know, the real question is about what benefit there is to running a UV unit long term.

I've run a UV sterilizer on my 125G since I set it up about four years ago. I initially got it because I did not fully understand how it would help me and thought that it would prevent algae. I know now that the only type of algae that it can really prevent is green water and that it does very little against other types.

I would argue that it does have other long-term benefits, the best of which is a healthy, nearly disease and parasite free environment for my fish *knocks on wood*. I have not had a sick fish or case of ick or any other parasite since I set the tank up. I can guarantee that this is not due to any strict quarantine procedures on my part because I am not very cautious at all when it comes to quarantining new fish.

Another excellent benefit of UV sterilization is water clarification. Along with good filtration my UV unit helps keep my water crystal clear. I am still amazed at how clear my tank is when I get up in the morning to look at it. I am a big fan of UV and will use it on any large tank I set up from now on.

Excellent feedback!

This is what I was looking for. Thanks!!

I've just set up a 48x20x30" 125gal in our showroom for just over a month now and I can tell you that I'm off to get a UV unit next week. It always has a 'haze' of greenish algae in the water despite the CO2, great water param's, substrate, lighting etc.. I know this will clear the situation to crystal clarity.
Did the same thing on my 800 gallon pond by adding a 18 watt sterilizer and the results are no sick fish and crystal clear water.
A worthy investment in my books for sure.

A few months ago I got an internal filter by Aquael (Unifilter) that has two UVC led's installed inside of it. I was a little skeptical since it was so cheap (< $50) and since very few places sell UVC LED's. However prior to getting it I was having continuous problems with 'flashing' (sign of parasites) as well as recurring bouts of ich for months. I didn't have the money to invest in an expensive UV sterilizer so I decided to try this one. Since I put it in, I have had absolutely NO flashing or ich recurrences so I have to conclude that it works. I'm definitely not removing it anytime soon.