differnt salts

[JOSH]

between all the salts, kents, instant ocean, seachem, is it just a matter of prefrence or do some salts benefit certian things?

[Ruth]

Oh man that is a can of worms to open up!
I think people have different systems and some salts seem to work better for them that others. Others, like myself, have had bad experiences with a particular brand of salt so choose to use others.
I think as a general rule when you mix up your new salt water and heat and airate it you should do calcium, alk/dhk, and magnesium tests on it. If it is close to the levels you are trying to achieve or can be easily tweeked to meet the levels you are looking for then that is the salt you should use.
Price is only one factor to consider when purchasing a salt mix. If you are going through additives, test kits etc. and time to acheive the mix you desire then perhaps it is time to re-think the salt mix.