Instruct: Classify Amazon reviews into positive or negative sentiment
Query: becareful

this powerhead i ran it in my 55 gallon and it sucked up alot of my fishes. I was wondering where all my fish went and when i decided to check the powerhead ... they were all stuck in there. It was really gross and i was shocked ... this is the reason why i gave it one star. However, if you run it with a sponge filter it's fine, but small fishes like neons and guppies got stuck in that green part. I guess with big fishes this is fine, but with small fishes you guys have to run it with a sponge filter.