I like the Orange spot goby - Valenciennea puellaris
Small fish that enjoys sifting the sand
Get a sea cucumber
I have to say, in a tank the size of Matt's you will see that sand shifting star all too often, it will be starving very slowly
Same goes for a Cucumber I think.
I only buy stuff that will be able to live in my tank indefinitely, so I suppose nausarrius (spelling?) snails are my best bet. Anyone know where I can get some?