I would like to point something out about using plain old table salt.
Iodine isn't the best for fish, but even if you get the non-iodized, there are still anti-caking agents in cheap table salt like Yellow Prussate of Soda, which can be very harmful through prolonged exposure (to both fish and people!)
A better option is to go to any store that carries bulk foods and get a bag of natural sea salt. It's only a teeny bit more expensive, and way healthier. I use natural sea salt for my own food too, so I always have it on hand if I need some for an aquarium to treat an illness.
Iodine isn't the best for fish, but even if you get the non-iodized, there are still anti-caking agents in cheap table salt like Yellow Prussate of Soda, which can be very harmful through prolonged exposure (to both fish and people!)
A better option is to go to any store that carries bulk foods and get a bag of natural sea salt. It's only a teeny bit more expensive, and way healthier. I use natural sea salt for my own food too, so I always have it on hand if I need some for an aquarium to treat an illness.