Feed Health Tracker

Feed pH. If you can only measure one thing, measure that. pH out of range causes lockout, which looks like every deficiency simultaneously and gets misdiagnosed constantly. An accurate pH measurement on feed water prevents about 70% of the nutrient-related problems home growers encounter. EC is the next most important — it prevents nutrient burn and underfeeding. Runoff measurements are a distant third; they're diagnostic for troubleshooting but not required for a healthy grow if your feed pH and EC are dialed.

Several causes. Mild drift downward (up to 0.3): roots producing organic acids during active nutrient uptake — healthy. Mild drift upward (up to 0.3): calcium being released from the medium or slight lockout starting — watch. Severe upward drift (0.5+): significant calcium buildup or medium breakdown — flush required. Severe downward drift (0.5+): medium breakdown (old coco), bacterial contamination, or severe root stress — investigate root health and medium age. If it's your first time measuring runoff and the delta is mild, don't panic — observe over 2–3 feedings to confirm the trend.

Both cause lockout, but they lock out different nutrients. High pH (above range) locks out iron and micronutrients first, leading to upper-leaf yellowing with green veins. Damage appears quickly (days) but recovery is fast once pH corrects. Low pH (below range) locks out calcium, magnesium, and phosphorus — the structural nutrients. Damage takes longer to appear but is harder to recover from because calcium deficiency causes permanent damage to forming tissues. If you have to pick an emergency to resolve first, correct low pH. But ideally, correct both immediately.

pH meter: weekly for $15–30 pens, every 2–4 weeks for $100+ meters (Apera PH20), monthly or less for Bluelab. EC meter: monthly — they drift slower than pH pens. Before any critical decision (like deciding whether to flush), calibrate first. A bottle of pH 4.0 and pH 7.0 calibration solution costs about $8 total and lasts 6–12 months. It's the cheapest insurance against phantom nutrient issues in your entire grow.

After. Always after. Nutrients shift pH themselves — usually downward, sometimes up depending on the base ratios. If you pH your water to 6.0 first and then add nutrients, the nutrients will shift it to 5.5 or lower. Order: fill reservoir, stir in nutrients in order (cal-mag first, then base A, base B, additives), wait 10 minutes for full mixing and chemistry to settle, then measure pH and adjust with pH Up or Down as needed. Final stir, measure again, feed.

Flush. Runoff EC at 2× feed EC means salts have accumulated significantly in the medium — every feeding is now adding to a toxic reservoir the plant is actively trying to avoid drinking. Flush with pH-adjusted plain water at 2× the pot volume (for a 3-gallon pot, run 6 gallons through). Collect runoff throughout the flush and measure EC; stop flushing when runoff EC drops below feed EC. Resume feeding at 70% of your normal strength for the next 2 cycles to give the plant a buffer. Investigate why salts built up — usually too-high feed strength or insufficient runoff during normal feedings.

Soil is a buffered medium — organic matter, clay, and microbial communities resist pH change and keep the root zone near the soil's natural pH (6.5–7.0 for most potting soils). That's why soil growers target 6.3–6.8 feed pH: they're matching what the soil is going to do anyway. Coco is inert — no buffer, no biology to mediate. The pH at the roots is whatever you feed. Coco also has a calcium exchange behavior where it displaces calcium ions — which naturally pulls root-zone pH slightly lower. Feeding at 5.8–6.2 matches where iron and phosphorus availability overlap, giving the widest nutrient availability window in an unbuffered medium.

Three tells. Test against calibration solution. A pH meter reading 7.0 solution as 6.8 is off by 0.2 — that's lying to you by 0.2. Recalibrate or replace. Test against a second meter. If you have two pH pens and they disagree by more than 0.1, one is lying. Test both against calibration solution to find which. Compare to plant behavior. If your meter says pH 6.0 (perfect) but plants show classic pH lockout symptoms (upper leaf chlorosis in hydro, cal/mag deficiency in soil), your meter is probably wrong and your actual pH is elevated. Cheap pH pens (under $20) are the most likely culprit — they drift dramatically and many are poorly calibrated out of the box. Budget another $80 and upgrade to an Apera PH20 or similar; it pays for itself in one avoided crop disaster.