Big Lake vs Ely Lake
Water quality, depth, fish species, and recreation comparison.
Big Lake and Ely Lake read the same on nutrients and algae. Both are in St. Louis County, Minnesota.
Big Lake and Ely 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. These two sit close on the readings, Big Lake versus Ely Lake. The deciding factors for a recreational visitor are likely physical (depth, access, fish species) rather than water-quality differences.
With readings this close, the choice between the two lakes turns on non-water-quality factors: depth, fish species, public access, distance from home. The per-lake pages below cover all of those.
Big Lake
Moderate clarity, visible to about 8.2 ft.
Ely Lake
Crystal clear, you can see 17.1 ft down.
Side-by-Side Metrics
| Metric | Big Lake | Ely Lake |
|---|---|---|
| Water Clarity | 8.2 ft | 17.1 ft Better |
| Phosphorus | 14 µg/L | 7 µg/L Better |
| Chlorophyll-a (Algae) | 4.9 µg/L | 2.1 µg/L Better |
| Maximum Depth | 22 ft | 70 ft Better |
| Surface Area | 1,904 acres | 723 acres |
| Public Access | Yes | Yes |
| Fish Species | 8 | 14 Better |
| Trophic State | mesotrophic | oligotrophic |
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.
Swap a lake
Compare Big Lake or Ely Lake against a different lake.
Verdict
Both lakes earn the same Grade A. The tiebreakers come down to clarity (Big Lake: 8.2 ft, Ely Lake: 17.1 ft) and what you want from the lake. Big Lake has fewer fish species than Ely Lake.
Source: EPA National Aquatic Resource Surveys, 2026.