I have used Morton brand evaporated sea salt for many years without the slightest problem. There are purists who will not use this salt commonly sold in 50 pound bags. This evaporated sea salt has no additives and is typically used in water softeners and for melting ice on streets. I pay about $4.29 US per bag at the local Home Depot, much like a giant hardware outlet, which also sells lumber and tools. The salt containing the additive YPS is dangerous and must be avoided. Common table salt is usually iodized and is not recommended for aquarium use. Many food stores sell non-iodized salt but as you mention it often has an anti caking agent which can be bad for aquarium fish. The local aquarium fish stores which carry aquarium safe salt often sell it for many dollars per pound and if you use any quantity it is worth locating it in commercial size bags.