Mayflies
Stoneflies
Caddisflies
Gammarids
Small Ardennes tributary near the German border—intimate trout water with pocket water and short drifts perfect for a tight line. Wild brown trout with some stocking. Very flashy after rain when the slate geology drains fast.
- Slate
Rules at a glance
- Day tickets
Water temperature for Grayling
Warm — slow15°C est.ideal 4–14°C
0°14°28°
How to fish it · for Grayling
When
Midday window — grayling feed best from late morning into early afternoon.
Where
Work runs and glides — grayling shoal in the bottom third of the water column.
Method
Tight-line nymph the bottom third with weighted patterns.
Kit
10 ft #3 rod, floating line, long leader to 4 lb fluoro for nymphs.
Why this works
Good — water clarity is working for you, but time of day is the limiting factor today.
Likely species
Caddisflies
- Large sedgesMost likelyNearest relative#8–10 · AdultBig waked sedge in the last light and after dark.
- Net-spinning caddisAlso possibleLower confidenceNearest relative#12–14–16 · PupaWidespread riffle net-spinner; evening emergence.
- CapererAlso possibleLower confidence#10–12 · AdultBig autumn sedge; fish dry at last light.
- Green SedgeAlso possibleLower confidenceNearest relative#10–12–14–16 · NymphFree-living green caddis larva; fast stony riffles.
Hatch timeline · todayPeak at 6am
Hatch predictions
Today's headline hatch shown — see all 12 active hatches hour by hour as a supporter.
Start free trial14-day free trial. Cancel anytime.
Sub-surface · on the nymphunder the surface
Hatch predictions
Supporters see the full sub-surface read.
Start free trial14-day free trial. Cancel anytime.
Beyond the hatch · worth watchingambient prey(1)
Hatch predictions
Top prey shown — see all 2 as a supporter.
Start free trial14-day free trial. Cancel anytime.
Evidence
Survey-backed · regionalHigh confidence
Backed by regional invertebrate surveys; no sampling on this exact reach yet.
Through the year
0–3 scale · September highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Trout seasonSeason
1
2
2
2
2
2
1
March BrownHatch
2
3
2
Late March BrownHatch
2
3
2
Large Brook DunHatch
2
3
2
Large StoneflyHatch
2
3
2
Numbers are intensity 0 (none) to 3 (peak) — a guide, not a guarantee.
Ranked for today
Grayling fly box
A proper Ardennes river-trout pack for Wallonia, centred on clear to lightly coloured rivers with trout and some classic fly-fishing culture.
Hook 14–18 · Fly
in season · matches water height
Permits & access
Permit required — see local rules.
- Permis de pêche (Wallonia) / Visverlof (Flanders)
- Foreign anglers can purchase online or at post offices without residency.
What's coming
Plan ahead
5-day outlook
Other water nearby · 5
Gallery · 2
Terrain map
About this water
Water quality (WFD)
- Ecology: Good
- Chemical: Unknown
WFD classification · BERW06_AM05R
The full read · show the working · for Grayling · confidence 55%
How the 66 is built — score × weight = contribution
Temperature69 × 28%19.3
Flow80 × 22%17.6
Clarity85 × 18%15.3
Feeding Time10 × 13%1.3
Pressure80 × 7%5.6
Insect activity57 × 12%6.8
Conditions total= 66
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowproxy via Warcheproxy
Prey activitysurvey-backed invertebrate datasurvey
What would change the calculation
Cooler water — back toward the 4–14 °C ideal band — would lift the score and ease welfare.
The dawn and dusk windows score higher than the midday lull.
Directions
Seasons & zones
- Trout 3rd Saturday of March → 30 September
Related guides
Booking & contacts
Holzwarche
Small Ardennes tributary near the German border—intimate trout water with pocket water and short drifts perfect for a tight line.
Water temperature for Grayling
Warm — slow15°C est.ideal 4–14°C
0°14°28°
How to fish it · for Grayling
When
Midday window — grayling feed best from late morning into early afternoon.
Where
Work runs and glides — grayling shoal in the bottom third of the water column.
Method
Tight-line nymph the bottom third with weighted patterns.
Kit
10 ft #3 rod, floating line, long leader to 4 lb fluoro for nymphs.
Why this works
Good — water clarity is working for you, but time of day is the limiting factor today.
Likely species
Caddisflies
- Large sedgesMost likelyNearest relative#8–10 · AdultBig waked sedge in the last light and after dark.
- Net-spinning caddisAlso possibleLower confidenceNearest relative#12–14–16 · PupaWidespread riffle net-spinner; evening emergence.
- CapererAlso possibleLower confidence#10–12 · AdultBig autumn sedge; fish dry at last light.
- Green SedgeAlso possibleLower confidenceNearest relative#10–12–14–16 · NymphFree-living green caddis larva; fast stony riffles.
Hatch timeline · todayPeak at 6am
Hatch predictions
Today's headline hatch shown — see all 12 active hatches hour by hour as a supporter.
Start free trial14-day free trial. Cancel anytime.
Sub-surface · on the nymphunder the surface
Hatch predictions
Supporters see the full sub-surface read.
Start free trial14-day free trial. Cancel anytime.
Beyond the hatch · worth watchingambient prey(1)
Hatch predictions
Top prey shown — see all 2 as a supporter.
Start free trial14-day free trial. Cancel anytime.
Evidence
Survey-backed · regionalHigh confidence
Backed by regional invertebrate surveys; no sampling on this exact reach yet.
Through the year
0–3 scale · September highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Trout seasonSeason
1
2
2
2
2
2
1
March BrownHatch
2
3
2
Late March BrownHatch
2
3
2
Large Brook DunHatch
2
3
2
Large StoneflyHatch
2
3
2
Numbers are intensity 0 (none) to 3 (peak) — a guide, not a guarantee.
Ranked for today
Grayling fly box
A proper Ardennes river-trout pack for Wallonia, centred on clear to lightly coloured rivers with trout and some classic fly-fishing culture.
Hook 14–18 · Fly
in season · matches water height
Permits & access
Permit required — see local rules.
- Permis de pêche (Wallonia) / Visverlof (Flanders)
- Foreign anglers can purchase online or at post offices without residency.
What's coming
Plan ahead
5-day outlook
Other water nearby · 5
Gallery · 2
Terrain map
About this water
Small Ardennes tributary near the German border—intimate trout water with pocket water and short drifts perfect for a tight line. Wild brown trout with some stocking. Very flashy after rain when the slate geology drains fast.
- Slate
Water quality (WFD)
- Ecology: Good
- Chemical: Unknown
WFD classification · BERW06_AM05R
The full read · show the working · for Grayling · confidence 55%
How the 66 is built — score × weight = contribution
Temperature69 × 28%19.3
Flow80 × 22%17.6
Clarity85 × 18%15.3
Feeding Time10 × 13%1.3
Pressure80 × 7%5.6
Insect activity57 × 12%6.8
Conditions total= 66
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowproxy via Warcheproxy
Prey activitysurvey-backed invertebrate datasurvey
What would change the calculation
Cooler water — back toward the 4–14 °C ideal band — would lift the score and ease welfare.
The dawn and dusk windows score higher than the midday lull.
Directions
Seasons & zones
- Trout 3rd Saturday of March → 30 September
Related guides
Booking & contacts