EC & pH by Stage — Coco vs Rockwool
Parallel feed-EC, drain-EC and pH targets stage by stage for both substrates, plus the buffering physics that makes coco forgiving and rockwool unforgiving.
7 min read
Feed EC and pH are not one-size-fits-all — they move by growth stage, and they differ between coco and rockwool because of one physical fact: coco buffers, rockwool does not. Coco's CEC (~40–100 meq/100 g) holds and releases ions, so root-zone EC responds slowly and forgives mistakes. Rockwool has near-zero CEC: the slab EC tracks your feed and dryback almost directly — fast, precise steering with no safety net.
| Stage | Feed EC (mS/cm) | Root-zone / drain EC | pH — COCO | pH — ROCKWOOL | Daily dryback |
|---|---|---|---|---|---|
| Propagation / clone | 0.5–0.8 | ~1.0–1.5 | 5.8–6.2 | 5.5–6.0 (pre-soak to 5.5) | ~2–4% |
| Early / mid veg | 1.1–1.8 | ~2–3 | 5.8–6.2 | 5.5–6.0 | 5–10% |
| Late veg | ~2.0 | ~3–4 | 5.8–6.2 | 5.5–6.0 | moderate |
| Generative / stretch (fl wk 1–3) | 2.0–2.6 (HPS) / 3.5–4.0 (LED) | ~5–8+ (LED) | 5.8–6.2 | 5.5–6.0 | 15–30% |
| Peak / bulking (fl wk 4–7) | 2.4–2.8 | 6–11 (LED) | 5.8–6.2 | 5.5–6.0 | 8–12% |
| Ripen / fade (last 1–2 wk) | 0.5–1.0 | declining | 5.8–6.2 | 5.5–6.0 | 15–30% (rockwool 4–6% overnight) |
The rest of this lesson is for members
Unlock every department, SOP, calculator, and setpoint table — plus Leaf, your AI consultant, and interactive diagnostics.
- All 11 departments
- Coco & rockwool tracks
- The full SOP library
- Leaf AI consultant
Unlock full access membership from $490/yr · or own it for life