Hey craig130170 -
Welcome to the board.
Since no one has responded, I'll give it a shot -
MA 3.1 works fine on W7 64 (at least it does for me on both of my systems).
Install MA 3.0 beta on your system (remember, it really isn't a "beta" in the sense that it may be "buggy"). You only have to copy one file frm the MA 3.1 download - "MarineAquarium3.scr" to the same place that the MA 3.0 beta file will be.
Then, sit back and enjoy the new stuff.
I know you think you understand what you thought I said,
but I'm not sure you realize that what you heard is not what I meant!