I had something (I think a tube anemone) stir up or release some unknown substance while I was watching my tank and instantly went into panic mode. Well I had planned to do a small H2O change this weekend so it was no biggie since I already had bought the premade water from Petsmart. I also had saltwater from the LFS with some ro/di. Of course the bottles of Caribsea Sea Pure water from petsmart dont have any type of protective cap, Just a regular twist off top. The first bottle tested fine with pH and salinity so I poured it right in. Assuming the other was ok I started to pour it in right behide it. After slowly pouring 1/4 of the second bottle in I noticed a few tiny bits of charcole floating around in the container. Panic mode time again. Stopping I grabbed my cheap floating lever hydrometer for a quick not so accurate test. It was reading a salinity of 1.028 if not more. I am guessing some sorry individual did a switch-a-roo with some of his old bad water, because I noticed it to be a tad darker yellow after I tested it. Yes I have tested some other pre-made water Made with the Petco name, and they were not dead on with pH and salinity like their box said, but then they came with protective caps and I had the confidence to know that they were not tampered with. I just had to adjust the water to my standards. So if anyone here is going to purchase premade saltwater, look for containers with some type of tamper proof opening. I am cool with it though because I know how things will come back to haunt you eventually.