My Giraffe is about 17" and eats large tetra cichlid sticks and sinking pelleted food. He fights for his share at the surface with the RTC, O, and a vieja. The Giraffe is a excellent scavenger vacuuming the gravel and shoveling it out his gills. Mine likes to play with the oscar and they are always sloshing water around. I'm not sure how long a grow out from 3" will take but you'll need as big of a tank with good filtration that you can afford.