Stoping Nemo And Gobies Geting Into The Overflow Box?

[humpy_the_humphead_wrasse]

ok so since putting gutter guard on the overflow, nemo and my 2 coral gobies are nightly getting themselves stuck in the overflow box, what can i do?? i have gutter guard on it but theyr still getting in there

 

[xxBarneyxx]

Stick a weir comb across it or maybe some eggcrate?

 

[humpy_the_humphead_wrasse]

well egg crate is basically the same as the gutterguard im using now i think. im not sude what a wier comb is but ill look it up.

im thinking of getting some net messing and clipping it over the edges like with the gutter guarde but running it up to the top of the tank hence stopping them getting onto the top of the wier or into it