Some Questions about Saltwater Setups

[jah29]

So I've been doing freshwater setups for a couple years now but I'm pretty new to saltwater...

I just got a 120g that I would like to make into saltwater..
I do not plan on doing a reef aquarium, just live rock and fish

These are my questions:
1) Do I need an RO system, or can use well water?
2) Do I need a protein skimmer even though it will be a fish only tank?
3) Do I need an overflow box and sump? (I have a rena xp3 and fluval 205 that I was planning on using for filtration)

 

[TaratronVaeVictus]

Yes on the protein skimmer. That I would say is kinda needed for most any marine tank over 20 gallons. The sump, no idea, and well water versus RO would depend on your water. I know here in AZ we have high phosphates in our well water, which means lots of food for marine algae, and not the pretty kind.