Instruct: Classify the given Amazon review into positive or negative sentiment.
Query: Complete Junk!

I am on my third one of these. Amazon was kind enough to replace the first two. They finally gave up and refunded my money. Amazon was very good in how they handled this at each stage. They even paid to overnight UPS ship one of the replacements, even though the cost of the item was far less and didn't warrant it. That said the stone itself is junk. Each time it broke apart and disintegrated into gravel in my tank.