In answer to all your questions, 1st of all I think it would be ok in your 20 for 3-6 months. They are currently eating ground up flakes, and I've started to power feed them for growth. The fish in my avatar is a catfish, in which a Red Snakehead bit in half........I would probably give you 2 GT's in case one did make it, but you have to figure that these are the four final surviovors of an original several hundred so they have to be tough cookies....