trying to set up a 55g reef need some advise

Hi i just purchased a used 55g tank on craigs list. it came with some filtration but i dont think its going to work. i want to run a reef and fish tank. it doesnt have a built in overflow and I cant afford to mod it and put a sump in. I have a fluval canister filter for my smaller 28g tank. Now heres my question has anyone used a sunsun canister filter? they're real cheap and I can buy one that has a 9watt uv starilizer in it. It's supposed to pump 370 gph. Do you think this will be sufficient? Also... they make a model without the sterilizer what is it for? And, do I need one in a reef tank?