The same salt that costs 10 times as much as regular salt. I use iodized salt.
Grain of salt trivia: Your local Dollar Tree may carry small bags of pink Himalayan salt mined in and imported from Pakistan. Seems like a great deal for an otherwise expensive product. The problem is that Pakistan uses TNT to mine their salt, so much that one of those trendy salt lamps will trigger TSA’s explosives sensors if brought back into the U.S.
Stop doing that. Use celtic. Then sea salt. The Iodine added. Not a natural one at that.