Lifegard UV Advice, 3" or 5" Diameter

[WhyMe?]

Research and equipment gathering phase for 500g display, 250-300g sump, future grow out/frag tank 120-150g. Total water volume is 900-1000 gallons. Starting live rock, fish only, stability than SPS corals. Regarding UV want clear water, algae control as priority.
Most likely going with Lifegard UV. Recommendations on size? Lifegard recommends Pro-Max 3", 90W but I am thinking the 120W version.
Questions:
1. Do I run TWO UVs at different flow rates? one for clear water/algae control and other for parasite/bacteria control?
2. If one, 90W or 120W?
3. NO REPLY yet from Lifegard on 3" or 5" diameter version. Besides diameter, what is disadvantage/advantage of 5" over 3"?
seems higher flow rate for 5" and I would think MORE contact surface area on 5".

Thank you.

 

[blaxsun]

Myself, I'd run a pair of 90Ws in parallel and plumb them so you can turn one off for maintenance if need be. I'd run them both with phasers set to kill.

 

[MarineandReef Jaron]

1. Do I run TWO UVs at different flow rates? one for clear water/algae control and other for parasite/bacteria control?
2. If one, 90W or 120W?
3. NO REPLY yet from Lifegard on 3" or 5" diameter version. Besides diameter, what is disadvantage/advantage of 5" over 3"?

1. I run only a single UV. If you want to use 2 that is not a problem. I just personally would use one and pick parasites or bacteria. I personally mainly run UV for algae and bacterial control.
2. The price difference is minimal so I would go 120 as long as you can fit it.
3. Lifegard has told me that the only reason they make a 5in is because competitors make a 5in. The 5in is better because more water is exposed to UV light at the same flow rate. However, the water is farther from the lamp so the exposure is not as intense. This is the reason that they don't adjust the ratings up for the 5in units. If you have the money for a 5in then go with it but the 3in are just fine. I have a 3in at home but would have gotten a 5 if I could fit it.