We had one that died - weird story.
They are AMAZING!
They are very observant: if you add a new item, they will be thoroughly inspecting it in moments.
They react to you VERY much, even when tiny.
They get dark when stressed - nice alert for their owner.
Mine darkened when he was hungry!
It is VERY easy to overfeed them. You want his tummy to get just a little round.
They learn to hand feed in a day.
They need a LOT of water compared to some fish, and are incredibly territorial (increasing with age).
They are very messy so frequent water changes are important to their stress levels.
They go from freshwater fish to brackish to saltwater.
I will send you an awesome site for research.