Mandarin Pair spawning in the wild, near the bottom of the page.
Google Image Result for http://www.islandream.com/photos/mandarin_fish02.jpg
"I also agree with the mandarin being a better choice, peaceful, beautiful, great to watch. Question: how many can you actually have in a tank? I am thinking of another. As long as I have more than enough copepods reproducing in a separate tank, they would be fine, right? Or am I linited to just 1 per tank? "
You can have a pair in a tank, and a 180 should be large enough to support 2. There are reports of spawning activity in captivity with a pair. The first dorsal spine is the distinction between male and female, on the male it is much longer than the rest of the dorsal spines, on the female it is just slightly longer.
Lined wrasses, 6line-4line-8line will all compete with mandarins for food and are all relatively aggressive for thier sizes.
Fairy wrasses (cirrhilabrus sp) and flasher wrasses (paracheilinus sp) are generally more peaceful. Both fairy and flashers require a quarantine period because they are prone to internal parasites, flashers also tend to be light sensitive out of shipping and will want to be acclimated in a dark environment.