Blackduck Lake vs Gull Lake
Water quality, depth, fish species, and recreation comparison.
Blackduck Lake and Gull Lake both received the same overall water quality grade of C (Fair). Both are in Beltrami County, Minnesota.
Blackduck Lake and Gull 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 are within a letter of each other on the rubric — Blackduck Lake (C) versus Gull 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.
Blackduck Lake
Murky, only visible to about 6.2 ft.
Gull Lake
Moderate clarity, visible to about 7.9 ft.
Side-by-Side Metrics
| Metric | Blackduck Lake | Gull Lake |
|---|---|---|
| Overall Grade | C (Fair) | C (Fair) |
| Water Clarity | 6.2 ft | 7.9 ft |
| Phosphorus | 34 µg/L | 26 µg/L |
| Chlorophyll-a (Algae) | 12.3 µg/L | 6.3 µg/L |
| Maximum Depth | 28 ft | 23 ft |
| Surface Area | 2,711 acres | 2,256 acres |
| Public Access | Yes | Yes |
| Fish Species | 16 | 13 |
| Trophic State | eutrophic | 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 (Blackduck Lake: 6.2 ft, Gull Lake: 7.9 ft) and what you want from the lake. Blackduck Lake supports more documented fish species.
Source: EPA National Aquatic Resource Surveys, 2026.