Tommy Field's solo homer leading off the sixth gave Salt Lake a 4-3 lead, which the Bees extended to 8-3 in the seventh by parlaying four hits and two errors by Tacoma into four runs.
From there, Salt Lake held on for its division-clinching win.
The Bees close out the regular season with a four-game series against Reno, starting Friday night at Spring Mobile Ballpark. Salt Lake is 7-5 against the Aces this season, including 3-1 at home.
Manager Keith Johnson has decided on three-fourths his pitching rotation for the final series, starting with righthander Matt Shoemaker (11-13) on Friday night.
Johnson will go with Tommy Hanson (0-2) on Saturday night and Billy Buckner (7-3) on Sunday afternoon.