Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Crashed my tank

I have a 75gal mixed reef tank that was doing great as a bare bottom tank. Wanted to add a little sand just for aesthetics, so I added only 15 lbs to make a 1/2 inch layer. Next day my SPS are all bleached out, LPS are all closed, and my softies are shrived or detached. I would never recommend that anyone put this in there marine tank.