I almost lost one of my African Dwarf Frogs due to my filter intake. Had to shut off the filter because the frog's backside was sucked up against the intake diffuser. At full flow, my Fluval 306 pulls a LOT of water. I created an outer basket around the intake with some netting and a couple of pringles can lids. Now the frogs hang out on top of it like it's special frog couch...