Do you find that the northerns become too fishy tasting later in the year? So far we have enjoyed them throughout the summer from Sak.
A fellow in Ohio was able to obtain some fertile tilapia and kept them in a large tank at school for an FFA project or such until his pond was warm enough to stock. They kept his pond algae free and spawned a few times and made bass food. End of summer, they caught as many as they could before cold killed them, between he and his friends fishing them out and the bass eating them, it worked well.