Ok, so more on the Dead Sea Bath Salts. I missed an important bit in my blog post yesterday. So I've edited it to add in the answer to the jetted tub question . . .
(here in case you missed it: http://randomsuds.blogspot.com/2014/07/dead-sea-salts-they-are-not-dead.html)
Top question - can they be used in a jetted tub? The answer is a very definitive, um, "maybe." First and foremost, it's important to check with your spa manufacturer since the internal working of each one can be different. You want to make sure that using the salt in your jetted tub will not void your warranty or get you in "hot water" so to speak. But having said that, the salt is all-natural, unrefined, with no additives and goes through an extra inspection process to remove any little rocks or foreign bits. They dissolve so quickly and easily that by the time you can drop your towel, the water will be silky smooth, and with a quick swish, you will be able to tell if there is a tiny little pebble on the bottom somewhere before turning on the jets. If you've used bath salts in your tub before, these will be no more risky. You are probably the bigger expert on how your particular spa works, way more than I am. But I've been assured that for most circumstances they will be perfectly fine.