A 3 pound tilapia is over a foot long and could not turn around in a 10 gallon tank. Systems that can support 1 pound per 2 gallons require pure oxygen. I'd push it to no more than 1 pound to 5-7 gallons of water with a standard aquaponics setup.

You can certainly use a small tank with smaller fish. I keep 10 O. mossambica in a 20 gallon tank. I use my DIY bead filter for the particulates.