Big Fish Lake vs Grand Lake
Water quality, depth, fish species, and recreation comparison.
Big Fish Lake has a higher water quality grade (A, Excellent) than Grand Lake (C, Fair). Both are in Stearns County, Minnesota.
Big Fish Lake and Grand 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. Big Fish Lake (A) is materially cleaner than Grand Lake (C). 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 grade gap is decisive — Big Fish 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?
Big Fish Lake
Crystal clear, you can see 20 ft down.
Grand Lake
Moderate clarity, visible to about 8 ft.
Side-by-Side Metrics
| Metric | Big Fish Lake | Grand Lake |
|---|---|---|
| Overall Grade | A (Excellent) | C (Fair) |
| Water Clarity | 20 ft | 8 ft |
| Phosphorus | 9 µg/L | 27 µg/L |
| Chlorophyll-a (Algae) | 1.8 µg/L | 8.5 µg/L |
| Maximum Depth | 70 ft | 34 ft |
| Surface Area | 557 acres | 651 acres |
| Public Access | Yes | Yes |
| Fish Species | 15 | 14 |
| Trophic State | oligotrophic | eutrophic |
Bold value = better for that metric (lower phosphorus / chlorophyll = cleaner; higher Secchi / depth / species count = better).
Verdict
Big Fish Lake wins on overall water quality with a Grade A versus Grand Lake's Grade C. Water clarity: 20 ft vs 8 ft. For fishing diversity, Big Fish Lake also leads with 15 species.
Source: EPA National Aquatic Resource Surveys, 2026.