Skimmer. If you can save a little more get the best skimmer you can afford, this is the classic case of "you get what you pay for". IMO a Seaclone is a decent skimmer. If you have room get the 150. If you've got a bit more $ go for a CPR Bak Pak, yada, yada, yada. While a skimmer might pick out some floating debris, they primarly remove dissolved organics, so the detrius that settles to the sand will be processed. Anyway that's what the sand critters are for (not to discount the need for good water movement).
Good hunting!