Fannie Lake
Isanti County, Minnesota360 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Fannie Lake. Here is what has been measured.
- Eutrophic
- Impaired · Nutrients (phosphorus, nitrogen)
- Eurasian watermilfoil
- 33 ft max depth
- Public access
Fannie Lake in Isanti County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 6.9 ft visibility. Phosphorus: 35 µg/L. Chlorophyll-a (algae): 9.3 µg/L. Maximum depth: 33 ft. Surface area: 360.01 acres.
Minnesota DNR's Targeted Survey on June 27, 2022 caught 2.50 walleye per gill net at Fannie Lake. DNR survey details →
Fannie Lake is a 360-acre productive, nutrient-rich eutrophic lake in Isanti County, Minnesota with a maximum depth of 33 feet. Overall water quality is improving over recent sampling years. The lake supports 13 documented fish species including black bullhead, black crappie, and bluegill. Public access is available with 2 public boat landings. Compared to the 16 other monitored lakes in Isanti County, Fannie Lake ranks #8 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-17. Methodology: how these readings are compared.
Fannie Lake covers about 360 acres in Isanti County. It has 2 public boat landings, so a lakefront rental is not the only way to get a boat on the water. If you are planning to stay, you can search lake houses and cabins around Fannie Lake on Vrbo, or look for a hotel room near the lake on Booking.com or Expedia.
What Fannie Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch2 documented ramps
- Fishing13 species recorded
- Deep water33 ft surveyed max depth
Swimming conditions
Readings onlyRecreation use not supported
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Fannie Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether Fannie Lake is safe to swim in today is a call for the Minnesota Pollution Control Agency and the Minnesota DNR and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Fannie Lake
These are the measurements Minnesota PCA publishes for Fannie Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Moderate clarity, visible to about 6.9 ft. Phosphorus 35 µg/L. Chlorophyll-a 9.3 µg/L. TSI 52.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 6.9ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 35µg/L | Fair GoodFairPoor |
| Chlorophyll-a (algae) | 9.3µg/L | Fair GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 52 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Fannie Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Fannie Lake typically sits around 70°F at the surface in September. Summer average is about 76°F. Usually warmest in Jul (about 79°F) and coldest in May (about 61°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (61°F) to its warmest (79°F).
Typical surface water temperature by month, from 18 field readings (2016–2025) via the EPA Water Quality Portal. See the full Fannie Lake water temperature breakdown →
Minnesota DNR's Targeted Survey on June 27, 2022 caught 2.50 walleye per gill net at Fannie Lake.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Fannie Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is improving. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
10 surveys on file from MN DNR Fisheries. Most recent: 2022-06-27 (Targeted Survey).
10 surveys on file · most recent 2022-06-27 (Targeted Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Bluegill | 39.64 | 2–7 in 2022-06-27 | 0.14 lb |
| Black Bullhead | 15.66 | 5–15 in 2022-06-27 | 0.6 lb |
| Largemouth Bass | 14.98 | 4–19 in 2022-06-27 | 1.03 lb |
| Black Crappie | 6.99 | 5–9 in 2022-06-27 | 0.18 lb |
| Yellow Perch | 5.06 | 5–7 in 2022-06-27 | 0.09 lb |
| Golden Shiner | 4.26 | 5 in 1996-06-25 | 0.04 lb |
CPUE = catch per unit effort, fish caught per net per set in a standardised survey. It measures abundance, not size, and is not a weekly bite report.
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.
Bluegill
Black Bullhead
Largemouth Bass
Black Crappie
From the 2022-06-27 survey
Fannie Lake is a 366-acre lake located in Isanti County that has been assigned to lake class 34. The lake is managed primarily for Northern Pike, Largemouth Bass, Black Crappie, and Bluegill. To assess the current population, a population assessment was conducted from June 27 to 30, 2022 with standard lake survey…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Fannie Lake. 4 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — FannieFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Fannie (1854)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — FannieFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — FanniePublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
33 ft
Surface area
360 acres
Shoreline
6 mi
Littoral zone
85%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
12 sq mi
HydroLAKES / HydroSHEDS
Elevation
932 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Lake Fannie (Northeast)Public
- Fannie Lake (East)Public
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Fannie Lake
Compare lakeside cabins, hotels, and vacation rentals near Fannie Lake in Isanti 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 Fannie Lake
Prices for Oct 9–11, 4 adults. Change dates on the map below.
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Planning a whole trip? See where to stay at Minnesota’s top lakes →
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Fish Species
Click a species to see every lake where it is documented.
Fishing Fannie 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.
Water Quality Trend: Improving
Based on 6 years of monitoring (2020–2025).
Water clarity
Stable6 years
Phosphorus
Stable+0.25 µg/L/yr4 years
Chlorophyll-a
Improving-1.34 µg/L/yr4 years
EPA Impairment Status
Fannie Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
Designated uses not supporting: Recreation.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN30-0043-00 · Official waterbody report
Nearby Lakes in Isanti County
Frequently asked questions about Fannie Lake
Where is Fannie Lake?
- Fannie Lake is a lake in Isanti County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Fannie Lake?
- Fannie Lake in Isanti County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 6.9 ft visibility. Phosphorus: 35 µg/L. Chlorophyll-a (algae): 9.3 µg/L. Maximum depth: 33 ft. Surface area: 360.01 acres.
Is Fannie Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Fannie Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
What is the water temperature of Fannie Lake?
- Fannie Lake typically sits around 70°F at the surface in September, from 18 EPA Water Quality Portal field readings (2016–2025). That is a typical value for the month, not a live reading.
How deep is Fannie Lake?
- Fannie Lake has a maximum depth of 33 feet. The lake covers 360.01 acres.
What fish are in Fannie Lake?
- Fish species found in Fannie Lake include black bullhead, black crappie, bluegill, bowfin (dogfish), green sunfish, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, walleye, white sucker, yellow bullhead, yellow perch. Fannie Lake is located in Isanti County, Minnesota.
What did the DNR fisheries survey find at Fannie Lake?
- Minnesota DNR's Targeted Survey on June 27, 2022 caught 2.50 walleye per gill net at Fannie Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Fannie Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is improving. Catch rate is not a swim clearance and is not a weekly bite report.
Are there boat ramps on Fannie Lake?
- Fannie Lake has 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Lake Fannie (Northeast), Fannie Lake (East). Public access is listed as yes.
Can I fish at Fannie Lake?
- Fannie Lake has 2 documented boat landings in the USGS National Boat Ramps inventory. Seasons, size and bag limits, and whether you need a license are set by Minnesota's fish and wildlife agency, so check its current regulations before you go.
Explore Fannie Lake across LakeQuality
Depth, room, public access, and the state wake-sport rules
Fish species and the cleanest lakes across Minnesota
Fish species and best lakes in Isanti County
Species activity outlook by water temperature and season
Where to stay at Minnesota's top lakes, each with its readings
Lakes in the Rum River Watershed, ranked by water quality
Minnesota's cleanest lakes, ranked on agency measurements
More lakes in Minnesota
State Parks Near Fannie Lake
Other Lakes in Minnesota
Eutrophic Lakes in Minnesota
Where this data comes from
38 measurements from 2 monitoring stations, 2022–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA38 samples · 2022–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
- Phosphorus by Colorimetry
Monitoring station identifiers (2)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from 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