Big Sandy Lake
Big Sandy Lake in Aitkin County, Minnesota has a water quality grade of C (Fair). Water clarity: 4.5 ft visibility. Phosphorus: 30 µg/L. Chlorophyll-a (algae): 11 µg/L. Maximum depth: 84 ft. Surface area: 6124.86 acres.
- Clarity
- 4.5 ft
- Typical in August
- 76°F
- Max depth
- 84 ft
- Area
- 6,125 acres
- Type
- Eutrophic
- Trend
- ↑ Improving
- Public access
- Yes
- Ice-out
- Apr 21
- Open water
- 223 days
Next lake in Aitkin County
Free interactive depth-contour map of Big Sandy Lake, reaching a maximum surveyed depth of 80 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Minnesota DNR.
Big Sandy Lake is a 6,125-acre productive, nutrient-rich eutrophic lake in Aitkin County, Minnesota with a maximum depth of 84 feet (21-foot average). Water quality is graded C based on 2 sampling years through 2025. Overall water quality is improving over recent sampling years. The lake supports 22 documented fish species including bigmouth buffalo, black bullhead, and black crappie. Public access is available with 2 public boat landings. Compared to the 17 other monitored lakes in Aitkin County, Big Sandy Lake ranks #11 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-20. 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 4.5 ft. Phosphorus level: 30 µg/L. Chlorophyll-a: 11 µg/L. Trophic State Index: 54.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 4.5 ft | Not graded |
| Phosphorus | 30 µg/L | Fair |
| Chlorophyll-a (Algae) | 11 µg/L | Fair |
| Trophic State Index (TSI) | 54 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Big Sandy Lake
Compare lakeside cabins, hotels, and vacation rentals near Big Sandy Lake in Aitkin 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.
Top-rated places to stay near Big Sandy Lake
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Planning a trip? Cabins and lodging at Big Sandy Lake → · more Minnesota lake trips
Water Temperature
Big Sandy Lake typically sits around 76°F at the surface in August. Summer average is about 76°F. Usually warmest in Jul (about 77°F) and coldest in Oct (about 61°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 96 field readings (2022–2025) via the EPA Water Quality Portal. See the full Big Sandy Lake water temperature breakdown →
Blue-Green Algae (Cyanobacteria)
There’s no recent EPA CyAN cyanobacteria estimate for Big Sandy Lake — clouds, ice, or an off-season gap in coverage. The most recent reading was high (554,626 cells/mL) on November 1, 2025.
Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 84 ft |
| Average Depth | 21.4 ft |
| Surface Area | 6,125 acres |
| Shoreline Length | 57 mi |
| Littoral Zone | 54% |
| Public Access | Yes |
Recreation & Access
- Big Sandy Lake (East)Public
- Big Sandy Lake (South Central)Public
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Big Sandy 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
43 surveys on file from MN DNR Fisheries. Most recent: 2025-10-06 (Targeted Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Walleye | 63.48 | 0.66 lb |
| Yellow Perch | 21.10 | 0.3 lb |
| LGP | 12.94 | — |
| GOS | 11.57 | — |
| JND | 9.95 | — |
| Largemouth Bass | 8.67 | 1.65 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.
Walleye
Yellow Perch
LGP
JND
From the 2025-10-06 survey
Fall night electrofishing (EW) was conducted on 10/02/2025 (representative locations) and 10/06/2025 (standard locations) to monitor natural reproduction, recruitment, and specifically the abundance of young-of-the-year (YOY) and yearling (age 1) Walleye. Eight standard locations have been sampled annually since 2009…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Big Sandy Lake. 4 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — Big SandyFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Big Sandy (0119)Aquatic Plant Report · MN DNR LakeFinder
- —Aquatic Plant Report — Big Sandy (0152)Aquatic Plant Report · MN DNR LakeFinder
- —Public Water Access Sites — Big SandyPublic 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 | ↓ Declining | -0.087 m/yr | 6 |
| Phosphorus | ↑ Improving | -0.75 µg/L/yr | 5 |
| Chlorophyll-a | ↑ Improving | -0.49 µg/L/yr | 5 |
Ice Season
Historical ice data from Minnesota DNR (143 observations).
Estimated open water season: 223 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2024-03-16 (2024) | 2013-05-12 (2013) |
| Ice-In | 2002-11-13 (2002) | 2001-12-23 (2001) |
Most recent ice-out: 2025-04-14
EPA Impairment Status
Big Sandy 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 MN01-0062-00 · Official waterbody report
County Ranking
Ranked #11 of 18 lakes in Aitkin County
Nearby Lakes in Aitkin County
Frequently asked questions about Big Sandy Lake
What is the water quality grade for Big Sandy Lake?
- Big Sandy Lake in Aitkin County, Minnesota has a water quality grade of C (Fair). Water clarity: 4.5 ft visibility. Phosphorus: 30 µg/L. Chlorophyll-a (algae): 11 µg/L. Maximum depth: 84 ft. Surface area: 6124.86 acres.
Is Big Sandy Lake safe to swim in?
- Generally safe for swimming, moderate water quality. Big Sandy Lake has a water quality grade of C (Fair). Algae concentration (chlorophyll-a) is 11 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Big Sandy Lake?
- Big Sandy Lake typically sits around 76°F at the surface in August, from 96 EPA Water Quality Portal field readings (2022–2025). That is a typical value for the month, not a live reading.
How deep is Big Sandy Lake?
- Big Sandy Lake has a maximum depth of 84 feet and an average depth of 21.4 feet. The lake covers 6124.86 acres.
What fish are in Big Sandy Lake?
- Fish species found in Big Sandy Lake include bigmouth buffalo, black bullhead, black crappie, bluegill, bowfin (dogfish), brown bullhead, burbot, channel catfish, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, redhorse, rock bass, shorthead redhorse, silver redhorse, smallmouth bass, tullibee (cisco), walleye, white sucker, yellow bullhead, yellow perch. Big Sandy Lake is located in Aitkin County, Minnesota.
When does Big Sandy Lake thaw?
- Big Sandy Lake typically has ice-out around Apr 21. Ice typically forms around Nov 30. The open water season is approximately 223 days.
Does Big Sandy Lake have blue-green algae?
- There is no recent EPA CyAN cyanobacteria estimate for Big Sandy Lake (clouds, ice, or an off-season gap). The most recent reading was high (554,626 cells/mL). Blue-green algae can appear and clear within days, so check Minnesota's current advisory before swimming.
Are there boat ramps on Big Sandy Lake?
- Big Sandy Lake has 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Big Sandy Lake (East), Big Sandy Lake (South Central). Public access is listed as yes.
Explore Big Sandy Lake across LakeGrade
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Where this data comes from
597 measurements from 15 monitoring stations, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA597 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H 2 ~ Chlorophyll a-b-c Determination by spectrophotometer
Monitoring station identifiers (15)
- MNPCA-01-0062-00-220
- MNPCA-01-0062-00-223
- MNPCA-01-0062-00-226
- MNPCA-01-0062-00-207
- MNPCA-01-0062-00-206
- MNPCA-01-0062-00-205
- MNPCA-01-0062-00-221
- MNPCA-01-0062-00-208
- MNPCA-01-0062-00-203
- MNPCA-01-0062-00-213
- MNPCA-01-0062-00-217
- MNPCA-01-0062-00-218
- MNPCA-01-0062-00-212
- MNPCA-01-0062-00-222
- MNPCA-01-0062-00-102
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
Ice data from Minnesota DNR Climate