Moon Lake

Moon Lake sits at the top of the Minnesota PCA grading rubric with an A, a mark reached by the cleanest lakes in Minnesota. Sub-grades cluster within a single letter of each other, which usually means the lake is in stable trophic balance rather than fighting one specific stressor.

The lake's low TSI puts it in oligotrophic territory — the cleanest of the four trophic classes, but also the most vulnerable to nutrient-driven shifts. The lake bottoms out at 38 ft — a moderate depth that supports a warm-water fishery without the year-round cold refuge a deeper basin provides. Moon Lake covers 139 acres alongside 2.7 miles of shoreline — a mid-sized water that supports a working fishery without being so large that conditions diverge between basins. Moon Lake ranks 8 of 51 in Douglas County, putting it in the upper tier of locally monitored lakes.

Zebra mussel presence at Moon Lake means the lake's clarity numbers carry an asterisk — filtered water is not the same as nutrient-poor water. The fishery includes walleye alongside the lake's other 12 documented species — a notable draw for Minnesota anglers. Public access is available — the lake is on the Minnesota PCA public-access list. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.