Overflow grids and fry??

[fish_fi]

I have just recently bought a new tank which I am going to use as my adult community tank and I am going to use my tank which I have got my fish in at the moment as a breeding/nursery tank. The only problem is that my tank has a built in overflow box or at least I think that's what it is (I've attached a picture of it). I have had 2 sets of fry that were born in this tank and both sets ended up going in the overflow box as they are that small they just get sucked straight in, luckily none of the fry ever got stuck/killed in the grids but they easily could do. Could I put anything over the grids that will still allow the water to flow into it but block the fry from getting in there not only am I worried that they are going to get injured but it is a pain in the backside trying to get the fry out of there once they've gotten in there.
Any ideas would be grateful!
Fi

 

[Fishperson]

Chicken wire? An old sock or something maybe?

 

[Mr Fisher]

pantyhose