Red tail sharks still get way too big for a 10g, and so do spotted plecos.

Local crabs may very well be predatory, and the small fish you'll be able to keep in there would be food. A pair of ocellaris or percula (the clowns that require the least space) would still require a 20g minimum. The good news however is there are several options for a 10g saltwater. You could get a goby/shrimp pair (like a yashia goby with a randalli shrimp- symbiotic pairing) plus a neon goby (a fish that will even try to clean your hand during maintenance- very cute!). If you can find the space though, there are many more options with a 20g or 30g.

This is a pretty decent list of nano fish with fair tank requirements. Pick one or two of them. Some of them need a 20g, so avoid those. http://liveaquaria.com/product/aquar....cfm?c=15+2124