Dumbbell is right near the Crest Trail and pretty shallow near the shore.
Like most high likes in the area, they don't respond to lot's of pressure but certain it has a few fish.
Check out Cramer Lake on the way in.
With a good green trails map, you'll find lots and lots of lakes in the area but you'd need more than a day to explore.
I've fished lakes here and you'll find blanks and others excellent fishing, particularly if you get off the beaten path.
Bring lots of bug repellent! Last week at Leech Lake the camping found tons of mosquitoes!