In this field guide, we only address the species brown trout, grayling, and salmon. A general rule states that:
- The gravel fractions should be a mix of 10-50 mm.
- A certain amount of larger gravel (up to 100 mm) should be present to make the bottoms more stable.
- Larger fish, such as migratory brown trout and salmon, mean that you can/should use a larger proportion of the coarser gravel fractions compared to when focusing on grayling and resident brown trout.
If you do not add material from outside (when you have the opportunity to mix different fractions), you simply have to use the material available. You can partially sort the material using a clamshell bucket. If possible, you can further optimize the fraction using Hartijoki tools.
