Instruct: Classify the given Amazon review as either positive or negative.
Query: Don't use dark fountains

Petmate makes a great fountain, but their black model should be discontinued. It is impossible to tell if the water is clean by looking at it. When I went to wash this fountain, like I usually do every couple of weeks, there was a purplish color slim growing by the pump and the charcoal filter was covered with it. I think the pump motor might have been leaking (I'm not really sure). If I had their white fountain I would have noticed there was a problem with the water right away.