I've been using ME Coral alk, ca, mag. It's pretty good and you don't have to dose a ton to keep your levels up.
Wierd though if I dose 9ml of mag I'm at 1480 to 1500 on the Salifert test kit. My calcium I just couldn't get it up above 400. I was thinking about it, and my tank normally likes magnesium so I bump my mag dose to 40ml. Well the alk really rose and so did the calcium (I had to lower my dose right away). So I concluded my mag must of been lower than the test. The test for mag at 40ml is the same just under 1500. I thought do I have a bogus magnesium test kit, so I bought two more Salifert Mag test kits and got the same results. Wierd science going on in my tank I guess.