Doo-e,
As far as I know, the only difference between regular salt and "aquarium" salt is the iodine. Iodine can kill fish so it isn't added to this type of salt and you can use it to treat FW fish for ick etc. The difference between "aquarium" salt and the salt we use for reefing is that it has additives (ca, mg etc). I believe you could keep a SW fish alive using "aquarium" salt. Heck, what did they use 30+ years ago before Instant Ocean came around??
Christy
