Hey Dave,
The above advice is great
As for adding different clowns you might have a problem with the Tomato as she's ranked number two next to the Maroon for being the most aggressive in the clown family.
Last year I added a small(tiny) new born perc to my reef that already had a mated pair of skunks. This was no problem as the female skunk didn't even give the new born the time of day as she had a mate already. The only problem was that the perc wanted to hang out with the skunk pair and the male skunk responded with some jealousy, after a few weeks of minor nose pushing they all calmed down. The small perc now hangs out with a same sized green chromis
