Yup. The foam ring is for the sides which already only have pretty skinny gaps anyway.
I was going to use the 1/4" mesh I had used for my screen top. I don't think 1/4" openings would impair the flow much. Definitely less than the foam ring (slowing down intake should slow down output don't you think?)

I got my 4 anthias yesterday and while releasing them 3 went into the rock work for hiding - the fourth headed straight for the MP40!!!
:o

I had turned them down to slow and they had the foam covers on the side so it wasn't going as fast as usual. I also yanked off the dry side right away to shut down the wet side from spinning.
But it was still quite shocking (for both of us -the anthias and myself!)