Good advice, uber.
Be careful with anemones. While clowns do love them, they’re often a pain to take care of and keep alive for any decent period of time (depending on tankmates, setup, etc). I’ve heard many stories of them getting sucked into powerheads as well, so bear that in mind.
With marines, there’s so, so many choices and combinations, it’s often difficult to stock your tank. Because of the environment they hail from, in all it’s vastness, nearly all marine fish & inverts are very specific feeders and will only accept certain foods and in certain ways. Unfortunately, if you get multiple fish which rely on these same resources in the tank, it creates great competition between the fish. Making picking good combinations very difficult and compatibility charts hard to trust.
Also, bear in mind, if you decide to go for a fish-only setup (i.e. no live rock, no corals and only very hardy inverts), many fish will be unsuitable and liverock provides an invaluable natural food source and hiding place. Also, the amount of fish the tank can handle will vary.
So, whatever you do decide to go for, read, read and read some more. Find out what their temperament is like and what they eat.
My percula clown is quite aggressive and a strong competitor for food in my tank. I keep it with a Midas Blenny, a Firefish, a Bangaii Cardinal, a Sixline Wrasse, a Coral Beauty and a small group of Green Chromis in a 65 gallon reef setup. For me, the angelfish is the most aggressive, the clown, cardinal, blenny and wrasse coming close second and the firefish and chromis receiving most of the aggression from the others, which makes food competition harder for them. The problem is, in a reef setup, it’s nigh impossible to get a fish out without ripping it all apart to catch the bugger – so you want to make sure you’re choices are good before you put them in.
And no, as uber said, the nemo setup wouldn’t stand a chance in hell. Also, if you put a shrimp-controlled bubble-lava-fountain in with great intentions of a tribal-nemo-initiation, I’m afraid you’ll also be disappointed.