Big Fish Lake vs Koronis Lake
Water quality, depth, fish species, and recreation comparison.
Big Fish Lake has a higher water quality grade (A, Excellent) than Koronis Lake (C, Fair). Both are in Stearns County, Minnesota.
Big Fish Lake and Koronis 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. The grades are meaningfully apart: Big Fish Lake grades a A while Koronis Lake grades a C. 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 — 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 20.7 ft down.
Koronis Lake
Murky, only visible to about 6 ft.
Side-by-Side Metrics
| Metric | Big Fish Lake | Koronis Lake |
|---|---|---|
| Overall Grade | A (Excellent) | C (Fair) |
| Water Clarity | 20.7 ft | 6 ft |
| Phosphorus | 9 µg/L | 26 µg/L |
| Chlorophyll-a (Algae) | No data | No data |
| Maximum Depth | 70 ft | 132 ft |
| Surface Area | 557.31 acres | 3.0K acres |
| Public Access | Yes | Yes |
| Fish Species | 1 | 1 |
| 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 Koronis Lake's Grade C. Water clarity: 20.7 ft vs 6 ft. For fishing diversity, Big Fish Lake also leads with 1 species.