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LakeQuality

Agnes Lake vs Iron Lake

Water quality, depth, fish species, and recreation comparison.

Agnes Lake has a higher water quality grade (B, Good) than Iron Lake (D, Poor). Both are in St. Louis County, Minnesota.

Reviewed by LakeQuality Editorial Team · Updated

Both Agnes Lake and Iron Lake sit in Minnesota. A same-state comparison strips out the state-level water-quality regime as a variable: any grade differences here are about the lakes themselves, not the agencies grading them. The grades are meaningfully apart: Agnes Lake grades a B while Iron Lake grades a D. That two-letter spread reflects real underlying differences — different watershed inputs, different depth profiles, or different monitoring rigor.

For a recreational visitor, the wider grade gap is decisive — Agnes Lake is the better water-quality choice. For a researcher, the gap is the interesting part: what is different about the two watersheds, and which of those differences is mutable?

B

Agnes Lake

St. Louis County, Minnesota

Good clarity, visible to about 11 ft.

D

Iron Lake

St. Louis County, Minnesota

Murky, only visible to about 5 ft.

Side-by-Side Metrics

Source: EPA National Aquatic Resource Surveys, 2026.

Source: EPA National Aquatic Resource Surveys, 2026.

Source: EPA National Aquatic Resource Surveys, 2026.

Source: EPA National Aquatic Resource Surveys, 2026.

Source: EPA National Aquatic Resource Surveys, 2026.

Source: EPA National Aquatic Resource Surveys, 2026.

Source: EPA National Aquatic Resource Surveys, 2026.

Source: EPA National Aquatic Resource Surveys, 2026.

Source: EPA National Aquatic Resource Surveys, 2026.

MetricAgnes LakeIron Lake
Overall GradeB (Good)D (Poor)
Water Clarity11 ft5 ft
PhosphorusNo dataNo data
Chlorophyll-a (Algae)No dataNo data
Maximum Depth30 ft64 ft
Surface Area1.0K acres2.0K acres
Public AccessNoNo
Fish Species109
Trophic Statemesotrophiceutrophic

Bold value = better for that metric (lower phosphorus / chlorophyll = cleaner; higher Secchi / depth / species count = better).

Verdict

Agnes Lake wins on overall water quality with a Grade B versus Iron Lake's Grade D. Water clarity: 11 ft vs 5 ft. For fishing diversity, Agnes Lake also leads with 10 species.