Nope, whatever it wants to eat it will eat. There's no safe way to train it off live foods. Anything that moves is going to get grabbed, and if it "tastes" like food it's food. I have kept a nice crocea clam in the tank for over 3 months now and I finally had to move it today. My octopus ignored it all this time but today decided it was next on the menu. If you buy lots of shore shrimp as feeders, most of them will live for a while swimming around the tank.
They are creating a wikipedia TONMO list for answers to all these questions that tend to go overlooked in the general information.
There is a BRIGHT orange Caribbean starfish that goes by the common name of knobby seastar/starfish that can be knock your eyes out orange and is a terrific scavenger but not a threat to any medium sized octo (small babies may not be safe but I know there is not a problem with adult dwarfs). I have two in with Octane (there are a couple of pictures showing them in his thread). One is less brightly colored but still excellent for estetics as well as clean-up and they are day active, unlike the serpents. The will nibble at soft coral if not fed well so they are marginally reef safe but do very well in an octo tank (WITHOUT clams ;>) I would provide a link but Ken is out right now and they are not even on the out of stock list right now but other FL collectors may have some in stock.
It does require meaty foods so it is best to wait until your tank is well established and even until you have your primary critter before adding one or two but they will not disappoint. The clam comment by AM reminded me I had a picture still in my camera. Unfortunately, not a very good one. Forget the polyps, these will be removed shortly as Octane avoids them purposefully. There are a set of polyps in his tank that I will transfer with him as he often runs into them without issue and they just fold up to avoid the contact but these common brown obviously cause discomfort.
For some other minor interest, you can also add the red Caribbean mushrooms. They will not thrive with low light but they will survive and grow.