Trace Minerals?

I'm fairly new to this hobby (under a year) and I have been buying my salt water through a fish/coral store. The owner told me that once in a while I should be mixing my own salt water because it has more trace minerals, which the corals need... is this true?, and what kind of salt mix should I buy?

Thanks for your help

 

It is VERY true. He must be using a Marine grade salt without the buffered elements reefs need. You can also test for these elements and add them via dosing.

 

i use kent sea salt. do regular water changes and i dose nothing. coral is healthy as ever

 

I recommend Red Sea Coral Pro.