Crystal Lake
Crystal Lake in Blue Earth County, Minnesota has a water quality grade of F (Algae-prone). Water clarity: 1.5 ft visibility. Phosphorus: 172 µg/L. Chlorophyll-a (algae): 59.9 µg/L. Maximum depth: 8 ft. Surface area: 379.38 acres.
- Clarity
- 1.5 ft
- Typical in August
- 77°F
- Max depth
- 8 ft
- Area
- 379 acres
- Type
- Hypereutrophic
- Trend
- ↓ Declining
- Public access
- Yes
- Ice-out
- Apr 1
- Open water
- 233 days
Grade F measures nutrients and algae, not whether this is a good place for a cabin trip. Cabins and rentals near Crystal Lake →
Next lake in Blue Earth County
Crystal Lake is a 379-acre highly nutrient-loaded hypereutrophic lake in Blue Earth County, Minnesota with a maximum depth of 8 feet (8-foot average). Water quality is graded F based on 2 sampling years through 2024. Overall water quality is declining over recent sampling years. The lake supports 12 documented fish species including bigmouth buffalo, black bullhead, and black crappie. Public access is available with 1 public boat landing. Compared to the 4 other monitored lakes in Blue Earth County, Crystal Lake ranks #4 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-10-06. 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.
Algae and nutrients are often high — check current advisories before swimming. Skip the water if you see scum or a paint-like bloom
Water Quality Grade: F (Algae-prone)
Very murky, less than 1.5 ft of visibility. Phosphorus level: 172 µg/L. Chlorophyll-a: 59.9 µg/L. Trophic State Index: 73.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.5 ft | Not graded |
| Phosphorus | 172 µg/L | Poor |
| Chlorophyll-a (Algae) | 59.9 µg/L | Poor |
| Trophic State Index (TSI) | 73 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Where to stay near Crystal Lake
Compare lakeside cabins, hotels, and vacation rentals near Crystal Lake in Blue Earth 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. The water-quality grade measures nutrients and algae, not lodging — cabins and rentals around Crystal Lake are listed below.
Top-rated places to stay near Crystal Lake
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a whole trip? See where to stay at Minnesota’s top lakes →
Water Temperature
Crystal Lake typically sits around 77°F at the surface in August. Summer average is about 75°F. Usually warmest in Jul (about 77°F) and coldest in May (about 61°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 66 field readings (2018–2024) via the EPA Water Quality Portal. See the full Crystal Lake water temperature breakdown →
Blue-Green Algae (Cyanobacteria)
There’s no recent EPA CyAN cyanobacteria estimate for Crystal Lake — clouds, ice, or an off-season gap in coverage. The most recent reading was very high (1,584,893 cells/mL) on July 19, 2026.
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 | 8 ft |
| Average Depth | 8 ft |
| Surface Area | 379 acres |
| Shoreline Length | 5.5 mi |
| Littoral Zone | 100% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Crystal LakePublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Crystal Lake
DNR Fisheries Survey Summary
11 surveys on file from MN DNR Fisheries. Most recent: 2023-04-19 (Targeted Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Black Bullhead | 109.40 | 0.3 lb |
| Black Crappie | 20.82 | 0.27 lb |
| Walleye | 16.75 | 1.28 lb |
| Common Carp | 12.05 | 3.19 lb |
| Bluegill | 8.82 | 0.25 lb |
| Green Sunfish | 7.00 | 0.27 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.
Black Bullhead
Black Crappie
Walleye
Common Carp
From the 2023-04-19 survey
Two trap nets were set at Crystal Lake on 19 April 2023 to assess winterkill. Yellow Perch and Black Bullheads were abundant. A single Black Crappie and a single White Sucker were also sampled. We have reports of anglers catching Black Crappie from shore. Dead Common Carp were observed on the shoreline.
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Crystal Lake. 3 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — CrystalFisheries Lake Survey · MN DNR LakeFinder
- —Fish Stocking History — CrystalFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — CrystalPublic Water Access Sites · MN DNR LakeFinder
Water Quality Trend: ↓ Declining
Based on 4 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.087 m/yr | 4 |
Ice Season
Historical ice data from Minnesota DNR (15 observations).
Estimated open water season: 233 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 1911-03-20 (1911) | 2008-04-14 (2008) |
| Ice-In | 1996-11-12 (1996) | 2020-12-01 (2020) |
Most recent ice-out: 2021-03-23
EPA Impairment Status
Crystal Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN07-0098-00 · Official waterbody report
Regulated Pollution Sources Nearby
2 EPA-permitted facilities operate within about 5 miles of Crystal Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Poet Biorefining - Lake CrystalLake Crystal · 3.7 mi away · NPDES MN0067172Recent violation
- Lake Crystal WwtpLake Crystal · 0.6 mi away · NPDES MN0055981
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 5 lakes in Blue Earth County
Nearby Lakes With Higher Grades
Crystal Lake holds Grade F. One nearby lake has a higher nutrient-and-algae grade — useful for a swim day, not a reason to skip lodging here.
Nearby Lakes in Blue Earth County
Frequently asked questions about Crystal Lake
What is the water quality grade for Crystal Lake?
- Crystal Lake in Blue Earth County, Minnesota has a water quality grade of F (Algae-prone). Water clarity: 1.5 ft visibility. Phosphorus: 172 µg/L. Chlorophyll-a (algae): 59.9 µg/L. Maximum depth: 8 ft. Surface area: 379.38 acres.
Is Crystal Lake safe to swim in?
- Algae and nutrients are often high — check current advisories before swimming. Skip the water if you see scum or a paint-like bloom. Crystal Lake has a water quality grade of F (Algae-prone). Algae concentration (chlorophyll-a) is 59.9 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Crystal Lake?
- Crystal Lake typically sits around 77°F at the surface in August, from 66 EPA Water Quality Portal field readings (2018–2024). That is a typical value for the month, not a live reading.
How deep is Crystal Lake?
- Crystal Lake has a maximum depth of 8 feet and an average depth of 8 feet. The lake covers 379.38 acres.
What fish are in Crystal Lake?
- Fish species found in Crystal Lake include bigmouth buffalo, black bullhead, black crappie, bluegill, common carp, hybrid sunfish, northern pike, walleye, white crappie, white sucker, yellow bullhead, yellow perch. Crystal Lake is located in Blue Earth County, Minnesota.
When does Crystal Lake thaw?
- Crystal Lake typically has ice-out around Apr 1. Ice typically forms around Nov 20. The open water season is approximately 233 days.
Does Crystal Lake have blue-green algae?
- There is no recent EPA CyAN cyanobacteria estimate for Crystal Lake (clouds, ice, or an off-season gap). The most recent reading was very high (1,584,893 cells/mL). Blue-green algae can appear and clear within days, so check Minnesota's current advisory before swimming.
Are there boat ramps on Crystal Lake?
- Crystal Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Crystal Lake. Public access is listed as yes.
Explore Crystal Lake across LakeGrade
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Fish species and best lakes in Blue Earth County
Species activity outlook by water temperature and season
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Very high nutrients, dense algae, poor clarity
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Where this data comes from
40 measurements from 2 monitoring stations, 2021–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA40 samples · 2021–2024
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
Monitoring station identifiers (2)
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
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