For my AR380 and my Fluval 104 I put one of these over the intake - I take the plastic bit out first, need to clean them by squeezing them out in a bucket once a month, depending on your setup.
They are a Sicce replacement sponge, I buy them in packs of four.
I also use them for sponge filters by sticking an airstone down the plastic bit and putting a suction cup with the clip through the slots to stop the airstone from coming out and to stick it to the wall of the aquarium. If you have the airpump turned up quite high you can get a moderate current.
I have one currently running in a 13l tank with CPDs.