I had a tetra whisper filter that did this straight out of the box, brand new. It was horrible. I have two aqua-tech HOB
filters that came with my 5 gallon tanks and they do NOT do this. I have since learned that these are both made by tetra (basically the same design). I guess it is hit or miss, and you could always contact the manufacturer, but from now on I am sticking with Hagan filters.