Hydroponic Nutrient Ratio
Nutrient needed (g)
13157.9
PPM/gallon
263.2
How it works
Hydroponic plants receive all nutrients directly through water. The Hydroponic Nutrient Ratio tool converts concentrate ratios to reservoir volumes, calculates target EC from nutrient additions, and adjusts ratios between growth stages.
**Three-part vs. two-part nutrients** Two-part systems (A and B) separate calcium and sulfate/phosphate to prevent precipitation in concentrated stock solutions. Three-part systems (Grow, Bloom, Micro) allow independent adjustment for vegetative vs. flowering stages. Bloom formulas have lower nitrogen and higher phosphorus and potassium than Grow formulas.
**EC as a nutrient proxy** EC measures total dissolved ion concentration. Standard targets: seedlings 0.8 to 1.2 mS/cm, vegetative stage 1.2 to 2.0 mS/cm, flowering 1.6 to 2.8 mS/cm, fruiting 2.0 to 3.5 mS/cm. High EC can cause nutrient lockout. Flush reservoir with clean water if EC rises 20% above target.
**pH and nutrient availability** Even with perfect nutrient ratios, pH out of range locks out specific elements. Optimal hydroponic pH: 5.5 to 6.5. Below 5.5: calcium and magnesium become unavailable. Above 7.0: iron, manganese, and zinc precipitate.
**Reservoir management** Replace the full reservoir every 7 to 14 days to prevent salt buildup and pH drift. Top off with plain water between changes, as plants uptake water faster than nutrients, raising concentration over time.
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Frequently Asked Questions
- Change the full reservoir every 7–14 days in active systems. Indicators that change is overdue: pH swings more than 0.5 per day (nutrient imbalance or microbial activity), EC rises significantly despite normal plant uptake (salt accumulation), slimy or discolored roots (bacterial/algal growth), plant growth slowdown despite correct EC and pH. Between full changes, top off with plain water (not nutrient solution) as needed — plants consume water faster than nutrients, concentrating the solution over time. After topping off, re-check EC and pH. If EC is significantly above target despite topping off, partial change is needed.
- 1-part nutrients: most convenient, pre-blended for a single growth stage. Limited flexibility for adjusting vegetative vs. flowering ratios. Best for beginners or single-crop systems. 2-part (A+B): calcium is separated from phosphate/sulfate in the concentrates because they precipitate if combined at high concentration. A and B are mixed in equal parts when preparing the reservoir. More adjustable than 1-part. 3-part (Grow/Bloom/Micro): maximum flexibility — adjust ratios for each growth stage. Grow is high nitrogen; Bloom is high phosphorus/potassium; Micro contains calcium, iron, and micronutrients that can't be in Grow or Bloom concentrates due to precipitation. Common brand example: General Hydroponics Flora series.
- pH rise (common): plants uptake more anions (NO3-, H2PO4-) than cations, releasing OH- and HCO3- that raise pH. Also common in alkaline water (hard water) with high carbonates. Fix: use pH Down (phosphoric acid) to adjust, or switch to RO water to eliminate buffering carbonates. pH fall: plants uptake more cations (NH4+, K+, Ca2+) than anions, releasing H+ that lowers pH. Also occurs in warm, low-O2 reservoirs where microbial activity produces acids. Fix: pH Up (potassium hydroxide), improve oxygenation (add air stone), keep reservoir temperature 65–68°F to inhibit pathogens. Aim for daily pH variation under 0.3 units.
- Not necessarily, but high mineral content in tap water creates complications. Hard tap water (above 200 ppm or 400 µS/cm EC) starts the reservoir with significant dissolved minerals before nutrients are added — some may be beneficial (calcium, magnesium) but may skew your nutrient ratios. Test tap water EC before starting: if EC is above 0.3 mS/cm, consider RO water or blending tap and RO 50/50 for most crops. City water chloramine (not just chlorine) cannot be removed by letting water sit overnight — you need a carbon filter or RO for chloramine removal. Sensitive crops (strawberries, lettuce) are more affected by water mineral content than hardy crops (tomatoes, herbs).