Instruct: Classify Amazon reviews into positive or negative sentiment
Query: poor quality

this filter is great in concept but not in reality! it is poor quality, the gasket on the power head leaks every other time i open it up and i have to re seal again. also the valve block leaks air into the unit and it creates bubbles, the valve block also got stuck shut because the ball valve stripped out only after a few uses and i had to purchase new one for 25 bucks plus shipping. and there is a reason you can't find o-ring kit anywhere!. honestly every time i open for cleaning there is some difficulty in getting it running again. marineland is part of the largest aquarium supply group and i expect better from them.