Ml-Peterson Lake vs Ml-Thains Lake
Water quality, depth, fish species, and recreation comparison.
Ml-Peterson Lake and Ml-Thains Lake both received the same overall water quality grade of C (Fair). Both are in Mille Lacs County, Minnesota.
Both Ml-Peterson Lake and Ml-Thains 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. These two are within a letter of each other on the rubric — Ml-Peterson Lake (C) versus Ml-Thains Lake (C). The deciding factors for a recreational visitor are likely physical (depth, access, fish species) rather than water-quality differences.
With grades 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.
Ml-Peterson Lake
Moderate clarity, visible to about 7.4 ft.
Ml-Thains Lake
Murky, only visible to about 5.3 ft.
Side-by-Side Metrics
| Metric | Ml-Peterson Lake | Ml-Thains Lake |
|---|---|---|
| Overall Grade | C (Fair) | C (Fair) |
| Water Clarity | 7.4 ft | 5.3 ft |
| Phosphorus | 26 µg/L | 27 µg/L |
| Chlorophyll-a (Algae) | 3.9 µg/L | 3.9 µg/L |
| Maximum Depth | 42 ft | 42 ft |
| Surface Area | 128,250 acres | 128,250 acres |
| Public Access | Yes | Yes |
| Fish Species | 21 | 21 |
| Trophic State | mesotrophic | mesotrophic |
Bold value = better for that metric (lower phosphorus / chlorophyll = cleaner; higher Secchi / depth / species count = better).
Verdict
Both lakes earn the same Grade C. The tiebreakers come down to clarity (Ml-Peterson Lake: 7.4 ft, Ml-Thains Lake: 5.3 ft) and what you want from the lake. Ml-Peterson Lake matches its peer on species count.
Source: EPA National Aquatic Resource Surveys, 2026.