As long as it is real sea salt, it will be ok. Note however, that there is more to the salt mix than just salt. If you are running or going to run a reef, I would not recomend it at all. If you are doing fish only tank, than it might be ok, but you will have to deal with pH, and Alkailnity, and other stuff that is automatically incorporated into the design of the salt mix, buffers additives are already in the mix.can you use kitchen sea salt in an aquarium?
Also remember, that a lot of Kitchen/Table salt, whilst 'brewed' by evaporating sea water, it also contains anti-caking agents, thus no good for aquariums.
Both excellent points. I forgot about those, because I buy pure sea salt (there is nothing in it but evaporated sea water, containing all of the trace minerals you'd find in the sea it came from). I forget that Morton makes sea salt, as do a number of other brands, and they use varying levels of additives to make their products more "consumer friendly."and most people by iodized salt...if you must, at least get pure salt.