Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Does not work!!! Beware!!!

I have owned $7K reef aquariums for many years with zero fish deaths except to old age, grown corals, had lots of difficult freshwater fish as well, etc. I have been in the fish hobby for a long time. I swear to you, this device does not work. I bought this to help me monitor the cycling of my newest tank and I knew my tank had high ammonia just from looking at the tank and the little disk in the middle of this test was white (lighter than the yellow "safe" color). I poured tons of food into the tank hoping to get ammonia to rise...I then poured pure ammonia into the tank and this test DID NOT CHANGE AT ALL. When I held the test over a bottle of ammonia, it did...finally..change color. It does not work adequately and your fish will suffer and/or die if you rely on this.