I have two, want more.
They are just awesome. If your tank is big enough for them to zoom around in then definitely get some, as many as you can afford. Mine are always on the go, and go mental for food, I feed them sinking cichlid gold pellets and they seem to be doing great.
When annoyed they make a sound like a teensie little sewing machine and if you're holding them at the time you can feel the vibration. ( :roll: and sometimes they do it in the middle of the night just to make you wake up and think what on earth was that?! )
Be careful when netting them, their spines get caught, also their pectoral and dorsal fins are pretty sharp, be careful if holding them