These are a great fish.
I have read a max size of anywhere between 4 and 8 inches. I started with two and they are fantastic, however one has dissappeared a while ago. What caused it I am unsure as due to the fish in the tank, if a body falls at night, it'll be gone by morning...
However, I digress...
The fish are fantastic to watch, especially all the colours they display. My remaining one loves to hang around in floating plants and jump for my fingers at feeding if I'm taking too long putting the food in.
I have seen no aggression issues with other fish, but keep in mind what CFC said about breeding. I also haven't seen any real marking of territory either, though now he is the only one he may feel the whole thing is his.
Mine gets fed a variety of:
Flakes;
Carnivore pellets;
Catfish pellets;
Bloodworm;
Live shrimp;
Live crickets;
and takes all with gusto.