I'm pretty sure he is aware of that Alan, but what Matt has done is syphon the sand thru a sieve.
The sand has gone thru ok, but because of the pressure some of the eggs(the smaller ones) become jammed in tne mesh.
Thinking about it.
If the sand is put thru the net with shaking, like gold panning, then the pressure onto the eggs wouldn't force so many into the mesh, and those that do, wont be so tightly wedged.
I watched Aquanut do this the other day, and he had the same problem.
A bit of experimenting Matt and you'll get it right I think.