i have to state, once again, i DID NOT say it was impossible, or even hard. if you actually read what i typed, i said "i know this is a personal choice, but the first thing i would do is ditch the MG".
if someone would like to point out where i said that it was impossible, well, id still call you a liar cuz it didn't happen. i said it was personal choice, and after someone retorted when not actually reading my post, i clarified it more so. was it not good enough? let me try one more time and since apparently people cant research or even read a post right above their reply, ill spell it out....
MG comes hot out of the bag (as does FF), but like an above poster said, heavy in salt. you can grow in mg soil, you can use mg nutes, BUT they are easy to burn plants with, can easily cause a salt buildup, and (ill caps this so i dont get misunderstood again) IN MY EXPERIENCE the pH can be a bit off for what you want for MJ.
it can be done. this was not my point. my point was that it doesn't need to be done, especially considering that things like FF are as cheap as they are (in my area).
-edit- if you truly dont believe me when i say it is not usually chosen for a reason, just do a search, or better yet start a poll. most seasoned growers will tell you that they dont like it.
-edit2- and to be fair (i wont NOT knock myself) i also misread the OP's post. when he said mg i assumed he also meant his soil (via pots outdoors).