When I use Primer3 design tool and the default Primer3 uses [Mg++] = 1.5 mM, whereas the average concentration is 5 mM in PCR kits. This concentration has a huge effect on the Tm. There is a “Salt concentration” box. Testing primer set designs for accuracy has shown that making the “Salt concentration” value 60 mM can help correct the Tm's. My question is; when I set the “Salt concentration” at 60 mM should I also have to use salt in my reaction and what kind of salt ? and can I use other values than 60 mM salt? Anyone who has used this tool before?