UV Sterilizers and Powerhead Arrangements

[ronin33]

I just added my first fish into a 90 gallon, fish only aquarium w 90 lbs cured live rock. Have a 110 gallon rated sump w a Rio 2500 Watt pump (540 gallons/hr). Purchased 2 powerheads that cycle another 700 gallons/hr. Is there any particular way I should arrange them?
Are UV sterilizers neccesary? How do you grade them? Should they cycle a certain amount of water per hour for a given volume. What are reliable brands? Can they be put in the sump? Do they need to be on 24 hours a day? Thanks!