You're talking about the surface skimmer? Or the canister filter. Both show 350 for the model I have the skimmer not the canister though so I may not be much help if you're referring to the canister. However what I see occasionally if its the canister you can put the sample socks or pantie hose over the intake. As for the skimmer I'm not sure how you would go about keeping them from jumping into that...
So I found the UKAPS thread (or at least one of them) regarding the E 350 issue. It looks like the stainless steel (SS) mesh idea might be the best solution. These guys are using the kind of SS mesh that one would use with growing moss walls.
Where is a good source for buying mesh and size to keep Chilis out?
Easy fix. Get a plastic knife and cut the blade into small pieces that will fit in the skimmer openings. Use super glue to glue them in place. It makes the grooves half sized. I can show pictures if needed. Haven't lost a fish since doing it