Fluval Fx4/5/6 intake screen
For those of you wanting to keep fry and baby shrimp safe with a fluval fx canister or possibly other canister filters I have found an alternative to a sponge. Seeing as the gph of the bigger canisters are rather high I was looking for a really large sponge at my lfs when I stumbled upon a Marineland Carbon Canister (part # PA0145)
These are on amazon for about $15. I got a rubber o-ring from work that fits into the light gray, the inside of the extendable fluval intake, right where the OEM fluval "strainer" attaches.
The carbon container now has a very snug and water tight fitment with the fluval extension.
Furthermore because there is an inner an outer screen on the carbon cantainer you can add cores foam or any kind of filter media to the container and increase your filtering capacity.
The container even has a flat back so it fits flush against the back of the tank and the screen is small enough that it should keep pretty much anything from getting into your canister.