Walk into any hydroponic store and you'll see twenty bottles with cryptic numbers like "3-1-2" and chemistry-set names. Here's what you actually need to know.
N-P-K, decoded
Every nutrient label lists three numbers: Nitrogen (N), Phosphorus (P), and Potassium (K). They're the three nutrients plants need in the largest amounts.
- Nitrogen drives leafy green growth.
- Phosphorus drives root and flower development.
- Potassium drives fruit production and overall plant resilience.
Why two- and three-part formulas?
If you concentrate calcium and phosphates together in one bottle, they precipitate out as an unusable sludge. Splitting them across two bottles solves the chemistry — you mix them into water separately so they never meet at high concentration.
Which to buy
- General Hydroponics Flora Series — the industry standard three-part. Excellent for everything.
- MaxiGro / MaxiBloom — one-part powder. Cheap, simple, perfect for beginners.
- Masterblend 4-18-38 — DIY favorite for lettuce farms. Three components but cheapest per gallon mixed.
Don't use Miracle-Gro
It's designed for soil, not water. It lacks several micronutrients plants need in hydroponics and the nitrogen source isn't ideal.
The micronutrients
Calcium, magnesium, iron, manganese, zinc, copper, boron, molybdenum — every quality hydroponic nutrient includes them. If you're using RO or distilled water, you may also need to add Cal-Mag separately.
Frequently asked questions
How long does mixed nutrient solution last?
Refrigerated and sealed: about a week. In an open reservoir: 2–3 weeks before pH and EC drift too far.
Can I use organic nutrients hydroponically?
Yes, but you'll need a biological filter — organic nutrients can clog pumps and grow biofilm faster than synthetic.
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