Tragic Sea Hare death

[Chin_Lee]

I don't think its possible unless you use small mesh or enkamat to cover the top. Those slugs will try to go through any holes. I had one that got stuck in eggcrate when it tried going through a .5 x .5 square not realizing that its big butt is about 2"x2" big - kinda like the Santa Claus dilemma.

[muck]

Zip-tie some gutter guard over your eggcrate overflow top to help keep snails, hermits, fish and anything else out of the overflow.
You can pickup a roll at Home Depot or Rona for a few dollars.

[fishoholic]

You can also zip-tie on the plastic background matting used for needle point. You can find the sheets in the sewing section of wal-mart, the sheets are about $1.00 each. It works very well for not letting small fish/snails etc. to go through the overflow, however it does reduce the flow and needs to be cleaned often.