A lot of different soft corals will leach a toxin to kill competitors. You can offset this a bit with carbon changed regularly. See how it goes, and you may decide to go all one or the other.
Good starter SPS would be many of the montipora species (digitata, capricornis), hydnophora, scroll corals. You can try some acros, maybe buy some cheap browned out corals and see how they do.
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Brad
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