A ten gallon tank is small....and I personally wouldn't put two clowns in any tank smaller than 30 gal...but you may manage keeping two false perks (Amphiprion ocellaris) in the tank...but that would be about it...and really pushing the limits....
You could get by without a protein skimmer in a fish only tank...but a skimmer will help remove dissolved organics before entering the nitrogen cycle...The fact is a skimmer will help you keep your nitrates down...
Here are the recommendations for nano fish in small aquariums...
http://www.liveaquaria.com/product/scateg.cfm?pCatId=2124