Nelson's tells us to throw that foam thing away, and use just the plastic barrel with the slits. The foam collects too much gunk and clogs up quickly, putting quite a strain on your pump, which continues to try to suck water through the clogged foam.
Removing the gunk is the job of your filter. Gunk needs to get through the barrel cover, and to your filter, where the media will collect it, until you do your weekly cleaning by hosing it off.
The barrel filter I have is sufficient to keep fish from getting sucked into the filter. Occasionaly a tadpole will get through, but only the very small hatchlings.
Be sure to check your pump at least once a week, as some leaves might get through the slits in the barrel and get caught in the intake, restricting flow and straining the prump.
With my 950 gph pump, I'm able to fit my pinkie finger in the hole and pull out any debris. On the 700, the hole is too small, so I have to use a screwdriver to remove the screws holding the housing in place. 5 minutes, max.