Sea walnut I cannot say with any certainty that the snakeheads are not causing damage to the ecosystem. That is why I say anecdotal, it means my personal observation or unscientific.
But I do know what they eat I cut them open and examine the stomach sometimes, I do eat them from time to time very good tasting fish..frogs, toads, baitfish, water scorpions, baby swamp eels, and once a baby soft shell turtle. But what has surprised me is I have caught many baitfish I can catch the same in canals without snakehead.
Let me ask you are paddelfish like flying carp? I would love to have those in a pond I don’t believe I cannot acquire flying carp due to them being considered a invasive species much like snakehead.