i havent seen any aggro issues in my pond since i got all the fish in there, the only problem i have had was the first day the 3 jd's decided to use the skimmer and spillway like a slip and slide, and the largest of the 3 was laying on the floor behind the lower section, so i put in a grate to keep them in the upper, the next day when i came into the room the largest jack jumped out the side of the pond. i quickly put him back in. this morning i went down stairs to turn lights on and there he is dry as the desert laying on the floor. anyone else have a jd that was bound and determined to kill itself?