These rocks made my fish tank unbelievably dirty. I rinsed them off for what seemed like hours, and they just kept flaking and creating disgusting water. Once I thought they were washed enough and decided to use them, the tank looked like someone dumped a cup of mud into it in less than half an hour. The residue left on the inside of the tank after dumping it out was unbelievable, it took me an hour to rinse and wipe it clean, and it’s still not 100% gone. Waste of moneySee full review