Nutrient Mix Calculator

Three likely causes. Probe contamination — nutrient residue on the probe skews readings. Rinse probe with distilled water after every reading, store in storage solution when not in use. Temperature drift — EC readings shift ~2% per °C; most meters auto-compensate but older ones don't. Check your meter's ATC spec. Calibration drift — EC meters drift 3–5% per month. Calibrate monthly with a 1.413 mS/cm KCl standard ($10 bottle). If your meter shows 1.8 EC in a freshly-mixed batch where it showed 2.0 EC yesterday with identical recipe and water source, calibration is the first suspect.

Because we don't know what you originally added. If your mix is 1.5 EC and target is 2.0, you need to increase your existing nutrient content by 33% — but what that means in mL depends on how much concentrate you used in the first place. If you started with 10 mL of base, add another 3.3 mL. If you started with 40 mL (larger reservoir), add another 13.3 mL. The percentage is the universal answer; the absolute amount depends on your original recipe. Practically: add roughly a third more of each component you originally used, stir, re-measure, micro-adjust from there.

Technically yes, but practical issues stack up. A 3-gallon mix at 4.0 EC needs 3 gallons of plain water added to reach 2.0 EC — that's a 6-gallon final volume. Do you have a 6+ gallon mixing container? Even if yes, you've just made twice as much nutrient solution as you planned to feed. If you're feeding every 2 days, the extra won't keep — bacteria and algae colonize nutrient solutions within 48–72 hours at room temperature. Restarting a 3-gallon batch costs you the original nutrients (nothing worth capturing) but avoids the volume and storage problem. Tool's "consider restarting" alternate fires when dilution would push volume past 50% increase.

Evaporation. Water evaporates from open reservoirs; nutrients don't. The remaining solution becomes more concentrated — same total dissolved solids, less water, higher EC. Rate depends on reservoir surface area, room temp, humidity. Typical DWC tank can lose 5–10% volume per week. Top off with plain pH-adjusted water every 1–3 days — never with more nutrients unless you've confirmed plants are consuming them, which is a different question. Your plants also consume water and nutrients at different rates, so EC drift is a combined signal. DWC tanks: measure EC daily, top off with water if EC is rising, top off with fresh nutrient if EC is falling.

EC. Three reasons. It's the actual measurement — your probe measures conductivity in mS/cm, PPM is a derived estimate. It's unambiguous — 2.0 EC is 2.0 EC everywhere in the world; 1000 PPM depends on which scale you're reading. International grower communities standardize on EC — if you're reading guides from Europe or Australia, or talking to other growers online, EC is the lingua franca. Most modern meters let you switch between EC and PPM in settings; pick EC and don't look back. If your feed chart only shows PPM, use the Convert mode to translate once and write the EC on your printed chart.

Heavy water buffering. Hard tap water or high-alkalinity source water resists pH changes — the calcium carbonate buffer "eats" the first doses of pH Down before any actual pH movement happens. If you added 3 mL pH Down and the meter still reads 6.8, the water has absorbed those protons without a visible pH change. Two options: add more, in increments — another 2 mL, stir, wait 2 minutes, measure. Harder water can need 2–3× the tool's estimate. Or switch to RO — if you're doing this every feeding with heavy tap, an RO filter ($80–150 starter unit) pays back in pH stability and Cal-Mag-independent feeding. Our tool's estimate is calibrated to moderate water buffering; extreme waters require empirical adjustment.

Measure each time. Pre-mixed concentrate stock ("batch tank") feels efficient but creates three problems. Chemistry degrades — concentrated nutrients react with each other over time; a week-old concentrate mix has less bioavailable calcium and more precipitate sediment than a freshly-mixed solution. Precipitation — concentrated calcium nitrate and concentrated phosphate in the same container form calcium phosphate crystals that never redissolve. pH drift — concentrates shift pH within hours; dilute solutions are more stable. Commercial operations do use batch tanks but with rigorous separation (A-only tank, B-only tank, mix on the fly). For home grows, mixing fresh every feeding is faster than managing batch-tank problems.

Primarily synthetic. Organic nutrients (compost teas, fish emulsion, bat guano, molasses, worm castings) release nutrients through microbial decomposition over time — the EC reading of an organic "feed" doesn't correlate cleanly with how much nutrient the plant will actually access over the next week. EC meters read fully-ionized salts well; they under-read organic feeds because the nutrients aren't yet in ionized form. Organic growers often ignore EC entirely and feed based on plant appearance, compost tea recipes, and top-dress schedules. This tool works for any product where dose → predictable EC response, which is almost all synthetic salt-based nutrients and a few hybrid organic-synthetic lines.