Ml-Thains Lake
Ml-Thains Lake in Mille Lacs County, Minnesota has a water quality grade of C (Fair). Water clarity: 5.3 ft visibility. Phosphorus: 27 µg/L. Chlorophyll-a (algae): 3.9 µg/L. Maximum depth: 42 ft. Surface area: 128250.02 acres.
- Clarity
- 5.3 ft
- Max depth
- 42 ft
- Area
- 128,250 acres
- Type
- Mesotrophic
- Trend
- ↑ Improving
- Public access
- Yes
- Ice-out
- Apr 25
- Open water
- 222 days
Next lake in Mille Lacs County
Ml-Thains Lake is a 128,250-acre mesotrophic lake in Mille Lacs County, Minnesota with a maximum depth of 42 feet (29-foot average). Water quality is graded C based on 3 sampling years through 2024. Overall water quality is improving over recent sampling years. The lake supports 21 documented fish species including black bullhead, black crappie, and bluegill. Public access is available with 2 public boat landings. Compared to the 8 other monitored lakes in Mille Lacs County, Ml-Thains Lake ranks #4 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-10-08. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyModerate
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.
Generally safe for swimming, moderate water quality
Water Quality Grade: C (Fair)
Murky, only visible to about 5.3 ft. Phosphorus level: 27 µg/L. Chlorophyll-a: 3.9 µg/L. Trophic State Index: 50.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 5.3 ft | Not graded |
| Phosphorus | 27 µg/L | Fair |
| Chlorophyll-a (Algae) | 3.9 µg/L | Good |
| Trophic State Index (TSI) | 50 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Ml-Thains Lake
Compare lakeside cabins, hotels, and vacation rentals near Ml-Thains Lake in Mille Lacs 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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Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 42 ft |
| Average Depth | 28.5 ft |
| Surface Area | 128,250 acres |
| Shoreline Length | 105.5 mi |
| Littoral Zone | 26% |
| Public Access | Yes |
Recreation & Access
- IslePublic
- Voge OutdoorsSemi-private
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Ml-Thains 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
36 surveys on file from MN DNR Fisheries. Most recent: 2024-09-01 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Yellow Perch | 219.50 | 0.23 lb |
| Spottail Shiner | 73.62 | 0.02 lb |
| Walleye | 69.99 | 1.23 lb |
| Tullibee (Cisco) | 17.45 | 0.62 lb |
| Smallmouth Bass | 16.43 | 1.74 lb |
| Bluntnose Minnow | 13.53 | 0.01 lb |
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.
Yellow Perch
Spottail Shiner
Walleye
Tullibee (Cisco)
From the 2024-09-01 survey
Sampling Programs Mille Lacs Lake is one of ten lakes in Minnesota's Large Lake Program. These lakes have annual sampling of the fish populations, and frequent creel surveys. Specific to Mille Lacs Lake, sampling programs focusing on Walleye, Yellow Perch, Smallmouth Bass, and Northern Pike are conducted annually.…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Ml-Thains Lake. 5 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — Mille LacsFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Mille Lacs (0134)Aquatic Plant Report · MN DNR LakeFinder
- —Aquatic Plant Report — Mille Lacs (0337)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — Mille LacsFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — Mille LacsPublic 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 | +0.102 m/yr | 6 |
| Phosphorus | → Stable | +0.31 µg/L/yr | 5 |
| Chlorophyll-a | ↑ Improving | -0.4 µg/L/yr | 5 |
Ice Season
Historical ice data from Minnesota DNR (123 observations).
Estimated open water season: 222 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2024-03-16 (2024) | 2013-05-16 (2013) |
| Ice-In | 1996-11-19 (1996) | 2001-12-22 (2001) |
Most recent ice-out: 2025-04-18
Regulated Pollution Sources Nearby
2 EPA-permitted facilities operate within about 5 miles of Ml-Thains Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Isle WwtpIsle · 1.3 mi away · NPDES MN0023809Recent violation
- WahkonWahkon · 4.6 mi away · NPDES MN0047066
Facilities permitted to discharge under the Clean Water Act within ~5 miles; proximity does not by itself mean a facility affects this lake. Source: EPA ECHO (ICIS-NPDES), as of 2026-07.
County Ranking
Ranked #4 of 9 lakes in Mille Lacs County
Nearby Lakes With Higher Grades
Ml-Thains Lake holds Grade C. 2 nearby lakes hold higher nutrient-and-algae grades — useful for a swim day, not a reason to skip lodging here.
See full comparison →Nearby Lakes in Mille Lacs County
Frequently asked questions about Ml-Thains Lake
What is the water quality grade for Ml-Thains Lake?
- Ml-Thains Lake in Mille Lacs County, Minnesota has a water quality grade of C (Fair). Water clarity: 5.3 ft visibility. Phosphorus: 27 µg/L. Chlorophyll-a (algae): 3.9 µg/L. Maximum depth: 42 ft. Surface area: 128250.02 acres.
Is Ml-Thains Lake safe to swim in?
- Generally safe for swimming, moderate water quality. Ml-Thains Lake has a water quality grade of C (Fair). Algae concentration (chlorophyll-a) is 3.9 µg/L. Always check local health department advisories before swimming.
How deep is Ml-Thains Lake?
- Ml-Thains Lake has a maximum depth of 42 feet and an average depth of 28.5 feet. The lake covers 128250.02 acres.
What fish are in Ml-Thains Lake?
- Fish species found in Ml-Thains Lake include black bullhead, black crappie, bluegill, bowfin (dogfish), brown bullhead, burbot, common carp, green sunfish, hybrid sunfish, largemouth bass, muskellunge, northern pike, pumpkinseed, rock bass, shorthead redhorse, smallmouth bass, tullibee (cisco), walleye, white sucker, yellow bullhead, yellow perch. Ml-Thains Lake is located in Mille Lacs County, Minnesota.
When does Ml-Thains Lake thaw?
- Ml-Thains Lake typically has ice-out around Apr 25. Ice typically forms around Dec 3. The open water season is approximately 222 days.
Are there boat ramps on Ml-Thains Lake?
- Ml-Thains Lake has 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Isle, Voge Outdoors. Public access is listed as yes.
Explore Ml-Thains Lake across LakeGrade
Depth, room, public access, and the state wake-sport rules
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Fish species and best lakes in Mille Lacs County
Species activity outlook by water temperature and season
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Moderate nutrients, good water quality
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Where this data comes from
48 measurements from 1 monitoring station, 2020–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Mille Lacs Band of Ojibwe DNR/Environment
MLBO_DNR_WQX48 samples · 2020–2024
Analytical methods
- 4500 P E ~ Phosphorus in Water by Colorimetry- Ascorbic Acid Method
- 10200 H ~ Chlorophyll a-b-c Determination
- SM 4500-PJ and NO3-F
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
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory
Ice data from Minnesota DNR Climate