That mesh is ideal.
I found some in a skip once, but never used it.
When they get to the ball valve, they can't get away from the suction and the water goes into their gills backwards, in their gills, out of their mouth, it must be an awful death. My current tank makes it impossible for a fish to go into the weir.
The fish that was fighting flow for god knows how long was luckily a Green Chromis, which are like bullets, streamlined and fast, like a Tuna. Had it been a clownfish or something more docile, I doubt it'd have made it.