Can water flow be too slow for a UV sterilizer?

Every time spring/summer comes along, my tank gets more and more daylight. Every season, I have a problem with green water. I usually do water changes ever 2 or 3 days to somewhat alleviate the problem.

This season, i'm going to bite the bullet and pick up a UV. I've decided to get the 36w Coralife TT. Figured there's a chance I'll be building a bigger tank so may as well pick up a bigger unit from the beginning.

I have an old Eheim 2213 that has a flowrate of 115gph.

This will be set up in a 260gallon tank.

Is it possible that the UV will end up killing too much? ie. beneficial bacteria?

Your benificial bacteria is on your media not the water column. So the UV wont effect that.

UV's are more effective at lower flow rates so it will still be effective at 115gph. for a 36 watt Turbo twist, i'd have it at around the same GPH as the tanks its on... so something like 250-300gph would be better for it to battle the algae considering tank size...

UVs are good for little more than green water though...