In a marine aquarium your biggest concern is preventing the buildup of Nitrate. As such, you do not want to run an artificial biological filter. Instead, you should utilize a good protein skimmer, live rock, and a sand bed. The protein skimmer will remove orgainic waste before it has the opportunity to be broken down into Nitrates. The sand bed and live rock will function to remove Nitrate from the system.
A biowheel, canister filter, bioballs.... these really have no place in a marine system. You may want to utilize activated carbon or phosguard in a canister filter, but you do not want to use any type of biomedia. Your live rock will function biologically to remove ammonia, nitrite, and nitrate from your system, provided you have a nice layer of sand.
Your biggest concern needs to be the addition of a protein foam skimmer. This is the single most important piece of equipment in a marine aquarium.