They are triploids. I probably put too many in the lake but I got a bit panicked when after the pond redo the grass came back in a bad way. Before the redo, the carp never seemed to put a dent in the coontaiI which made me believe they might rather starve than eat that nasty stuff. I think I put 12 to 14 in at about 8 inches. I've caught three now while fishing with worms and powerbait for catfish and bluegill. I've thought about taking some out but as you said, I believe I will wait to see how the grass is over the next warm season.