Moon Lake
Moon Lake in Douglas County, Minnesota has a water quality grade of A (Excellent). Water clarity: 21 ft visibility. Phosphorus: 11 µg/L. Chlorophyll-a (algae): 1.8 µg/L. Maximum depth: 38 ft. Surface area: 139.09 acres.
- Clarity
- 21 ft
- Typical in August
- 72°F
- Max depth
- 38 ft
- Area
- 139 acres
- Type
- Oligotrophic
- Trend
- ↑ Improving
- Public access
- Yes
Next lake in Douglas County
Moon Lake is a 139-acre cold, clear oligotrophic lake in Douglas County, Minnesota with a maximum depth of 38 feet (19-foot average). Water quality is graded A based on 2 sampling years through 2025. Overall water quality is improving over recent sampling years. The lake supports 12 documented fish species including black bullhead, black crappie, and bluegill. Public access is available with 1 public boat landing. Compared to the 36 other monitored lakes in Douglas County, Moon Lake ranks #16 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-08-30. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyLimited data
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A (Excellent)
Crystal clear, you can see 21 ft down. Phosphorus level: 11 µg/L. Chlorophyll-a: 1.8 µg/L. Trophic State Index: 36.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 21 ft | Not graded |
| Phosphorus | 11 µg/L | Good |
| Chlorophyll-a (Algae) | 1.8 µg/L | Good |
| Trophic State Index (TSI) | 36 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay near Moon Lake
Compare lakeside cabins, hotels, and vacation rentals near Moon Lake in Douglas County, Minnesota — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
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Water Temperature
Moon Lake typically sits around 72°F at the surface in August. Summer average is about 71°F. Usually warmest in Jul (about 73°F) and coldest in Apr (about 48°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 126 field readings (2019–2025) via the EPA Water Quality Portal. See the full Moon Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 38 ft |
| Average Depth | 19 ft |
| Surface Area | 139 acres |
| Shoreline Length | 2.7 mi |
| Littoral Zone | 32% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Moon LakePublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Moon Lake
Invasive & Introduced Species
Red chips are ecologically harmful invasive species. Gray chips are stocked or introduced fish that aren't a current ecological concern.
DNR Fisheries Survey Summary
10 surveys on file from MN DNR Fisheries. Most recent: 2023-06-26 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| BNS | 78.40 | — |
| Largemouth Bass | 36.44 | 0.83 lb |
| Bluntnose Minnow | 19.88 | — |
| Bluegill | 16.83 | 0.22 lb |
| IOD | 15.66 | — |
| BKF | 15.44 | — |
CPUE = catch per unit effort, averaged across surveys (excludes juvenile shoreline seining). Higher CPUE = more abundant in standardized sampling.
Length Distributions
Number of fish caught at each inch class in the most recent survey that recorded lengths. Red dashed line marks an approximate trophy threshold for that species.
Largemouth Bass
Bluegill
From the 2023-06-26 survey
Moon Lake is a 126-acre natural lake located just southeast of Brandon in western Douglas County. Maximum depth is 38.0 feet. Average depth is estimated at 19.0 feet due to steep banks and a rapid drop off along much of the north, west, and south shorelines. Water quality is very good. Summer water clarity…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Moon Lake. 4 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — MoonFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Moon (0921)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — MoonFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — MoonPublic Water Access Sites · MN DNR LakeFinder
Water Quality Trend: ↑ Improving
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.351 m/yr | 6 |
EPA Impairment Status
Moon Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN21-0226-00 · Official waterbody report
County Ranking
Ranked #16 of 37 lakes in Douglas County
Nearby Lakes in Douglas County
Frequently asked questions about Moon Lake
What is the water quality grade for Moon Lake?
- Moon Lake in Douglas County, Minnesota has a water quality grade of A (Excellent). Water clarity: 21 ft visibility. Phosphorus: 11 µg/L. Chlorophyll-a (algae): 1.8 µg/L. Maximum depth: 38 ft. Surface area: 139.09 acres.
Is Moon Lake safe to swim in?
- Excellent for swimming, crystal clear water with minimal algae. Moon Lake has a water quality grade of A (Excellent). Algae concentration (chlorophyll-a) is 1.8 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Moon Lake?
- Moon Lake typically sits around 72°F at the surface in August, from 126 EPA Water Quality Portal field readings (2019–2025). That is a typical value for the month, not a live reading.
How deep is Moon Lake?
- Moon Lake has a maximum depth of 38 feet and an average depth of 19 feet. The lake covers 139.09 acres.
What fish are in Moon Lake?
- Fish species found in Moon Lake include black bullhead, black crappie, bluegill, green sunfish, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, walleye, white crappie, white sucker, yellow perch. Moon Lake is located in Douglas County, Minnesota.
Are there boat ramps on Moon Lake?
- Moon Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Moon Lake. Public access is listed as yes.
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Where this data comes from
120 measurements from 1 monitoring station, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA120 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
Monitoring station identifiers (1)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory