Meadowlark, I understand tilapia to be filter feeders. However, you report that you occasionally catch them on a fly rod. What do they eat other than filtered plankton and green plants? Do they ever take commercial pellets?
BTW, I have never seen a grass carp take a pellet but did catch one on a piece of nightcrawler. I'm wondering if the tilapia will starve out the grass carp. No problem; if the weeds come back, I will just get more tilapia.
