Yes, it is aquarium salt. I will have to try the rock salt though with my cichlids later just to see if it does the same result as the aquarium salt. I didn't even use that much. But the reason I added salt is because the person who bought them, and returned them back because it was too much for him, told me that in the process of moving, one jumped out of the container and was on the ground for awhile. This is the fish that got the fungus. But the other two, they seemed really stressed out, so I added just about 5 tablespoons on a 4x2x2 quarantine tank. Later that day, one fish was dead, the other has their tail end floating to the surface, and none of them was eating. But the end result was that they are all dead...and I was not happy. The species I was keeping were micropeltes, aka redline or giant SH, which to me are pretty hardy.