I've kept paddlefish, I had several for three years until I had to move and they didn't survive the move.
They eat floating pellets at the surface and will eat small fish, especially if the fish are in a school.
I kept mine in several containers from a 360 gallon outdoor vate to a 125 indoor aquarium.
Mine were supposed to be genetic dwarfs and over three years they never got more than about 11" long. Thier hatch mates that were not dwarfs attained a length of over 2 feet by that time.
What is your source? I'd like to have a few more to try in my 225.