I've raised Tilapia in ponds for many years and based on studying them here's my take:
Tilapia present some challenges. For one thing, they generally will not chase a fly. They will eat them but only if they don't have to chase the fly down. Secondly, they can not/ will not outcompete bluegills/sunfish for a fly...or any lure for that matter. They like to "sip" feed. So, any strategy for consistently catching them has to account for this behavior.
Every fall I stock my freezer with Tilapia...by then they are too large for most bass and are going to die anyway not to mention how good to eat they are. I look for a day after a cold front and draw the Tilapia into shallow water away from bluegills with range cubes. Then proceed to catch as many as I want to clean.
I like to use nymphs and have to put the fly right on their nose. They fight excellent.
This is the only circumstance I've been able to consistently catch them; otherwise its one here and one there but always only when the fly is presented right to them and no other predator fish are there to get it.
Pile of Tilapia: