If it's a blue throat I'd recommend getting a female if you can find one. They seem to do better in pairs or groups from everything I have read. My experience was that a single male did fine for a couple years and then just died randomly. I've read about this same type of experience from others as well.
Currently I have a humu and an assassi sharing a tank and they seem to keep each other occupied pretty well. They do have an occasional skirmish but that's about it. They go nuts for literally any type of food.
Urchins would be a fun feeding activity but it would get very costly. Cheapest and most fun solution is likely MORE TRIGGERS! :0) Just be careful with your choices.