Originally Posted by spittinfly
I thought you put a sponge filter on a line to keep fry from getting sucked up.
There are two kinds of sponge filters. It sounds like you're describing a prefilter, that slips over the intake of a more powerful filter and prevents fry from getting sucked up. This is just a stand alone sponge filter. You stick an air line to the bottom of that tube, and the rising air creates a current of water going into the sponge, up the tube, and out the 45 degree elbow. There's no impeller for fry to get chopped up in.