Shrimp in Overflow

I have a CPR90 overflow on my 15 gallon tank and for whatever reason I keep finding my shrimp in it. One actually was sucked down into my refuge and I will likely never find him again . Anyone have a suggestion from keeping them out? I did remove the grate that they include with the overflow due to it collecting tons of junk. Any other ideas? I did think about making a cover out of screen door material but not sure how that would impede performance.

Thanks!

 

put the grate back on. just have to clean it every week or so.

 

screen door material is going to collect a lot more debris than the grate. The white plastic things they sell at craft stores would work better than screen door material. I would get the one with the biggest holes.