Meadowlark, I originally got my first Pacu out of an Aquarium shop, 7 of them which were about a half pound at the time. When I purchased the land that my pond is on it had a half acre pond on it that had many of the local fish and some Tilapia in it. I was looking for a predator/sporting fish to stock and found these Pacu in the pet shop so decided to buy and release them. Later on I found peacock bass and the Pacu lost some of their appeal.
The Pacu are an extremely hardy fish, my wife and I caught each of these Pacu at least 3 or 4 times within the first couple of months they were released, many times they had swallowed the hooks which I had cut the line and released them. None ever died. The Pacu, 5 of the original 7 are still left and they are about 12 pounds now after 3 years, I have since bought 20 more last year and not totally sure, but believe they may have spawned as I have caught a few that are in between the two releases. My water stays turbid so it is difficult to see smaller fish in the water except for what you catch and at feeding time when they are near the surface. The Pacu stay in a school most of the time and seem to call each other with tail splashing (may also use this to ward off competing feeders). The large Pacu are easy to spot on the pond as they are usually close to the surface and create a large wake when they move around.
The Pacu will follow me around the lake like a pack of puppies looking for a food handout, since they stay close to the surface sure that they can spot people on the banks. Since the original ones started out in an aquarium I am not sure if their following is a native or trained instinct. Pacu seem to be somewhat smart in their schools, when I do catch one they often will not come near for several days, when they are spooked they all disappear together. They are very wise and can ID a bobber and or fishing line. When young they were a lot easier to catch! I often work outside Thailand (now in Afghanistan), upon returning to my pond I can usually get a hook up for a day or two...then they wisen up and stay that way. I feed floating pellets at times and will float a couple of pellets on a hook in the middle, when they are wise, will eat every other pellet and leave those on my hook floating.
They have become somewhat of a pain because of their teeth. Often I'll use light line (4-8 lbs) to try and catch the local fish or Tilapia and hook the Pacu, it usually ends in a good fight but broken off line! They are a powerful fish and will often jump as their dragging off line once or twice on the way out, never had them jump on the way in. Sometimes will use Spiderwire when fishing for them and have landed Pacu with that, but they will only bite when using that line when their guard is down. Up to about two pounds you should be able to land the Pacu with regular monofilaments. Have caught them on minnows and earthworms also, however that is at times when not feeding pellets.
My pond has not had any weed problems yet so really don't know what their preferences are on grasses. Probably with a year round stock of Pacu and Tilapia will never have a weed problem. As stated earlier cannot get Lotus plants to survive, have transplanted the Lotus twice, about 200 plants each time and they just disappear.
On eating quality, they are delicious however they do have a hairline bone.
If they have an unlimited supply of food they will become fatty. On their eating habits have never seen them become full when feeding pellets, they will come to the surface and swim around with their mouths open like a bucket loader!
Hope that this helps you get a jump start on your experiment, not nearly as much information on Pacu as there is on Tilapia on the net, so most of what I've stated has been my own observations. Keep us all posted on your trails, interested to see if the Pacu die off before or after the Tilapia in the winter and how much damage they do to the grasses.
