I use whatever I win, lol.
Just got done using Magnesion(brightwell), probably won't use it again due to low concentration.
I've used the AquaVitro one, worked well. Gets expensive though.
Currently trying BRS mag chloride. Instructions say to mix with the mag sulphate(epson salt) though.
I used to mix a few cups epson salt in my ato container. Worked well but was told to keep up on my water changes because of (forgot what Jon said, sure wish he'd login again)