Round Lake
Round Lake in Aitkin County, Minnesota has a water quality grade of A (Excellent). Water clarity: 14.5 ft visibility. Phosphorus: 10 µg/L. Chlorophyll-a (algae): 2.7 µg/L. Maximum depth: 125 ft. Surface area: 736.65 acres.
- Clarity
- 14.5 ft
- Typical in August
- 54°F
- Max depth
- 125 ft
- Area
- 737 acres
- Type
- Oligotrophic
- Trend
- → Stable
- Public access
- Yes
- Ice-out
- Apr 14
- Open water
- 240 days
Next lake in Aitkin County
Round Lake is a 737-acre cold, clear oligotrophic lake in Aitkin County, Minnesota with a maximum depth of 125 feet. Water quality is graded A based on 2 sampling years through 2025. Phosphorus level is improving over recent sampling years. The lake supports 18 documented fish species including black bullhead, black crappie, and bluegill. Public access is available with 3 public boat landings. Compared to the 17 other monitored lakes in Aitkin County, Round Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-24. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyLow algae
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)
Good clarity, visible to about 14.5 ft. Phosphorus level: 10 µg/L. Chlorophyll-a: 2.7 µg/L. Trophic State Index: 39.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 14.5 ft | Not graded |
| Phosphorus | 10 µg/L | Good |
| Chlorophyll-a (Algae) | 2.7 µg/L | Good |
| Trophic State Index (TSI) | 39 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay near Round Lake
Compare lakeside cabins, hotels, and vacation rentals near Round 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.
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Water Temperature
Round Lake typically sits around 54°F at the surface in August. Summer average is about 67°F. Usually warmest in Jul (about 76°F) and coldest in Aug (about 54°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 267 field readings (2017–2025) via the EPA Water Quality Portal. See the full Round Lake water temperature breakdown →
Blue-Green Algae (Cyanobacteria)
There’s no recent EPA CyAN cyanobacteria estimate for Round Lake — clouds, ice, or an off-season gap in coverage. The most recent reading was low (9,036 cells/mL) on April 25, 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 | 125 ft |
| Surface Area | 737 acres |
| Shoreline Length | 5 mi |
| Littoral Zone | 44% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- North Garrison BayPublic
- Round LakePublic
- Phil's Myr MarinaSemi-private
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Round 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
23 surveys on file from MN DNR Fisheries. Most recent: 2025-08-04 (Targeted Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| MMS | 121.61 | — |
| Smallmouth Bass | 64.48 | 0.95 lb |
| Bluntnose Minnow | 54.76 | — |
| Tullibee (Cisco) | 18.61 | 0.52 lb |
| Largemouth Bass | 14.06 | 0.82 lb |
| Bluegill | 13.99 | 0.12 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.
Smallmouth Bass
Tullibee (Cisco)
Largemouth Bass
Bluegill
From the 2025-08-04 survey
A temperature-dissolved oxygen (TDO) profile was collected on 8/6/2025 to measure the amount of thermal habitat available for Tullibee. The TDO3 (temperature at 3 mg/l dissolved oxygen) was determined to be 5.8 degrees C and comparable to previous assessments. While water from the surface to about 17 feet was warm,…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Round Lake. 4 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — RoundFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Round (0061)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — RoundFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — RoundPublic Water Access Sites · MN DNR LakeFinder
Water Quality Trend: → Stable
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | +0.039 m/yr | 6 |
| Phosphorus | ↑ Improving | -0.23 µg/L/yr | 6 |
| Chlorophyll-a | ↓ Declining | +0.11 µg/L/yr | 6 |
Ice Season
Historical ice data from Minnesota DNR (14 observations).
Estimated open water season: 240 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2017-04-05 (2017) | 2022-05-02 (2022) |
| Ice-In | 2002-11-21 (2002) | 2021-12-25 (2021) |
Most recent ice-out: 2022-05-02
EPA Impairment Status
Round 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 MN01-0204-00 · Official waterbody report
County Ranking
Ranked #1 of 18 lakes in Aitkin County
Nearby Lakes in Aitkin County
Frequently asked questions about Round Lake
What is the water quality grade for Round Lake?
- Round Lake in Aitkin County, Minnesota has a water quality grade of A (Excellent). Water clarity: 14.5 ft visibility. Phosphorus: 10 µg/L. Chlorophyll-a (algae): 2.7 µg/L. Maximum depth: 125 ft. Surface area: 736.65 acres.
Is Round Lake safe to swim in?
- Excellent for swimming, crystal clear water with minimal algae. Round Lake has a water quality grade of A (Excellent). Algae concentration (chlorophyll-a) is 2.7 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Round Lake?
- Round Lake typically sits around 54°F at the surface in August, from 267 EPA Water Quality Portal field readings (2017–2025). That is a typical value for the month, not a live reading.
How deep is Round Lake?
- Round Lake has a maximum depth of 125 feet. The lake covers 736.65 acres.
What fish are in Round Lake?
- Fish species found in Round Lake include black bullhead, black crappie, bluegill, bowfin (dogfish), brown bullhead, common carp, green sunfish, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, rock bass, smallmouth bass, tullibee (cisco), walleye, white sucker, yellow bullhead, yellow perch. Round Lake is located in Aitkin County, Minnesota.
When does Round Lake thaw?
- Round Lake typically has ice-out around Apr 14. Ice typically forms around Dec 10. The open water season is approximately 240 days.
Does Round Lake have blue-green algae?
- There is no recent EPA CyAN cyanobacteria estimate for Round Lake (clouds, ice, or an off-season gap). The most recent reading was low (9,036 cells/mL). Blue-green algae can appear and clear within days, so check Minnesota's current advisory before swimming.
Are there boat ramps on Round Lake?
- Round Lake has 3 documented boat landings in the USGS National Boat Ramps inventory. Named access points include North Garrison Bay, Round Lake, Phil's Myr Marina. Public access is listed as yes.
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Where this data comes from
120 measurements from 2 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
MNPCA120 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 (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
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