I understand Daggerfall Overlook has slaughterfish.
As far as this as a furnishing, it would not make sense as it would only affect a small area of the water feature and would not be limited to the water feature as I do not think Zenimax has programmed such controls.
That'd be cool. Could act as a trap for like a death maze or something.
I'd even cool with placeable mobs or bosses that don't give any exp or damage equipment or anything when fighting them. But maybe that's a little too far-fetched, lol.