what do you call the plastic cover you'd put over an overflow to keep out eels?

[michaelp]

I can't figure out what its called so I don't know how to buy it

Most people use it to put their frag posts in... it's a plastic grid, that you could put at the top of an overflow box to keep eels out.

 

[Jaftica]

eggcrate or light diffuser

 

[NL146]

You could also try gutter guard

 

[NYC Joe]

I think i have some extra lying around.
pm me

 

[masterswimmer]

You could also try gutter guard

+1, I like gutter guard better than the egg crate.

HTH
swimmer