| Hey Bill,
My take on UV's is, go big or stay home, although having one is better than not. I've got a 25 watt LG on my 135. I would have gone to the 40 if it fit under the stand. There's two reasons I feel the way I do about bigger is better. First, a bigger UV doesn't "killem" any deader but, it doesn't let any get by either. Too small of a UV unit may kill some but, not all. I've heard the "bugs" that get by alive have altered genes, DNA or something. It may render them harmless, maybe not. Second, UV bulbs lose power/effectiveness over time. The bulbs are supposed to be replaced every year. If you are getting 100% kill out of a 25 watt unit. That kill ratio will drop some over a year. If you have a 40 watt unit, you still get 100% kill. Because of the extra punch of the 40, I believe the unit will go two maybe three years and still be more effective than the 25. It's just conjecture/theory but, it seems logical, at least to me.
UV effectiveness also depends on flow rate. Pay attention to the recommended flow rate for what ever unit you decide on. A slower flow rate than recommended will guarantee a better kill rate but may be too slow for the size tank you have. Again, a bigger unit serves you better. You can push more water through, killing more "bugs". After all, that's what we use UVs for so, the more "bugs" you kill over a longer time-period the better off your system. That's why, "bigger is better" in my humble opinion.
Dick
__________________ Amphibious Reaching my 70th BD, I realize that I cannot help but grow old. However, I refuse to grow up!!! My wife would tell you, "He may be 70 but, He's going on 17". Life is wonderful with a woman like that. Our web site The Cultured Reef Our Talking Reef Forum The Cultured Reef Forum My tank journal Amphibious' 135 mixed reef. The Cutured Reef toll free number - 888 745-0449  Amblyeleotris randalli commonly called Randall's Goby. | 
