UV Sterilizers in freshwater tanks: useful tool or unnecessary?

[ohhfishhh]

I have been reading more about UV sterilizers for freshwater aquariums and I am curious how useful they actually are in a normal home setup.
From what I understand, UV only affects organisms that actually pass through the unit and receive enough UV exposure. That means it can help with things such as green water and some free floating microorganisms, but it is not a replacement for good filtration, maintenance, or quarantine.
One thing I find interesting is how much the flow rate matters. A faster flow gives the water less exposure time, while slower flow generally provides a higher UV dose. So I assume there is a big difference between using a UV mainly for water clarity and trying to reduce pathogens.
For those who have used one on a freshwater tank, what has your experience been? Did you notice a real improvement in water clarity or fish health, or did regular maintenance make more difference?
I would especially like to hear from people who have run UV continuously for several months rather than just using it during an algae or bacterial bloom.

 

[Rusty_Shackleford]

Last spring, after changing my light fixtures I had a green water bloom. It was nasty, like pea soup.
I franticly researched for a week or so before purchasing a UV unit. See here

In my research I learned a many things.
First there is a difference between flow rate and UV power.
In commercial applications like treating drinking water a high powered UV light is used. Why? Because that filtration is used as one time pass. The water only goes by the UV one time so it has to be powerful enough to damage whatever organisms it's trying to eradicate.
Notice I said damage and not kill. When your talking about bacteria, algae and such, the UV doesn't kill it, but it does mutate it so that it effects the reproduction of that organism.
In our aquariums we don't need as powerful a UV source. Our aquariums are closed systems. So our water passes through the UV light many times which accomplishes the same goal as one exposure to a higher powered UV source.

 

[MuddyWaters]

I have one and I use it when I need it. I haven't needed it in awhile (I'm better at balance now), but when I have had algae blooms it's the best thing ever.

I actually bought a pretty powerful one for my 75 gallon tank a few years back and was going to permanently install it in the out hose of the filter. I read, however, that it would increase the temperature of the water, so I decided not to and sent it back. The one I have is the "Mean Green Killing Machine." I read all kinds of stuff about them not being worth the money etc. etc, but my brother had a friend who said he had great results, so I bought one and I had the same results.

The thing about the stuff I read on the internet is that (and you guys know this) one person writes something negative who has some cache' or admiration from a group of followers and it gets parroted by Ladi-Dadi-and-Everybody as if it's the gospel. ONE sentence of real experience from someone is worth more than all of that, however.

I only use it when things get way out of whack, but when they do, it's a great tool to have.

 

[GaryE]

It can be useful for stopping disease transmission. With really delicate species, it can help a lot.

I never replaced my unit when the bulb burned out, but I should have. I would also use it on a 'when I saw a need' basis.