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Round Lake reads lower on nutrients and algae than Big Sandy Lake. Both are in Aitkin County, Minnesota.

Reviewed by LakeQuality Editorial Team · Updated

Big Sandy Lake and Round Lake are both in Minnesota — a same-state head-to-head where the comparison comes down to lake-specific differences in depth, watershed, and monitoring history rather than the broader state-level water-quality regime. Round Lake reads materially cleaner than Big Sandy Lake on nutrients and algae. A gap that wide is unlikely to close in a single year of remediation work; it reflects multi-decade differences in the lakes themselves.

For a recreational visitor, the wider gap in the readings is decisive: Round Lake has the lower nutrient and algae numbers. For a researcher, the gap is the interesting part: what is different about the two watersheds, and which of those differences is mutable?

Big Sandy Lake

Aitkin County, Minnesota

Murky, only visible to about 4.5 ft.

Round Lake

Aitkin County, Minnesota

Good clarity, visible to about 14.5 ft.

Side-by-Side Metrics

MetricBig Sandy LakeRound Lake
Water Clarity4.5 ft14.5 ft Better
Phosphorus30 µg/L10 µg/L Better
Chlorophyll-a (Algae)11 µg/L2.7 µg/L Better
Maximum Depth84 ft125 ft Better
Surface Area6,125 acres737 acres
Public AccessYesYes
Fish Species22 Better18
Trophic Stateeutrophicoligotrophic

A green ✓ marks the better value for that metric (lower phosphorus / chlorophyll = cleaner; higher Secchi / depth / species count = better). Surface area and trophic state carry no tick — a bigger lake is not a better lake.

Verdict

Round Lake reads lower on nutrients and algae than Big Sandy Lake. Water clarity: 14.5 ft vs 4.5 ft. For more fish-species variety, Big Sandy Lake edges ahead with 22 documented species.

Source: EPA National Aquatic Resource Surveys, 2026.