Does a 10G Aquarium Need Skimmer? Powerhead?

[skabooya]

good answers so far. You dont need a skimmer if your doing regular WC. As for the nem I wouldnt recommend one in such a small tank. They get big and a clown may or may not host in one. You also need to have a mature tank and strong light to keep one alive (takes a minimum of 6 months).
If you like the flowieness of a nem then look for another coral that does better in small systems and can be fragged easily to keep it in check. Maybe a torch?