Take a aqua clear mini sponge, take the scissors and nip down the center of it just enough to slip it over the intake. Make sure the foam is length wise up so it covers the whole intake. Been using this for several things in my tanks for years works like a charm and has no effect on the flow or working of the filter at all.
Just take off and rinse once in a while. Very easy to do.
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Bugsy.... 
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