Hydroponic Nutrients Complete Guide

Plants need food. In hydroponics, you're the chef. Understanding nutrients transforms you from someone following a recipe to someone who can diagnose and solve problems. This is the complete guide to feeding your plants.

## Quick Picks: Essential Nutrient Equipment

The honest truth: Following the bottle instructions at half strength will grow healthy plants. You don't need to understand everything in this guide immediately - but this knowledge helps when something goes wrong.

## The Basics: What Plants Actually Need

Macronutrients (needed in larger amounts):

Micronutrients (needed in trace amounts): Iron, manganese, zinc, copper, boron, molybdenum, chlorine. Quality hydroponic nutrients include all of these. Deficiencies are rare with decent nutrients but common with cheap or incomplete formulas.

## Understanding NPK Ratios

Every nutrient bottle shows three numbers like 5-5-5 or 3-1-2. These are the NPK ratio - the proportion of Nitrogen, Phosphorus, and Potassium.

Higher first number (N): Promotes leafy growth. Good for lettuce, spinach, herbs in vegetative stage.

Higher second number (P): Promotes root development and flowering. Good for fruiting plants starting to flower.

Higher third number (K): Promotes overall health and fruit development. Good for tomatoes producing fruit.

For most home herb and salad growing, balanced ratios work fine. The complexity matters more for optimising specific crops at specific stages.

## EC and TDS: Measuring Concentration

EC (Electrical Conductivity) and TDS (Total Dissolved Solids) both measure how much stuff is dissolved in your water. Higher numbers mean stronger nutrient solution.

Pure water: EC 0 / TDS 0 Tap water: EC 0.2-0.6 / TDS 100-300 (varies by area) Light feeding: EC 0.8-1.2 / TDS 400-600 Medium feeding: EC 1.2-2.0 / TDS 600-1000 Heavy feeding: EC 2.0-2.8 / TDS 1000-1400

Why this matters:

Too weak and plants grow slowly. Too strong and plants burn (brown crispy leaf tips).

Typical targets by crop:

A basic EC/TDS meter costs around £15-25 and removes all guesswork. One of the most useful tools you can buy.

## Feeding Schedules

Seedling stage (first 2-3 weeks): Quarter to half strength nutrients. Delicate roots burn easily. EC around 0.4-0.8.

Vegetative growth (until flowering): Full strength as plants establish. Higher nitrogen. EC as per crop targets.

Flowering and fruiting: Shift toward phosphorus and potassium. Reduce nitrogen slightly. Same or slightly higher EC.

General principle: Start weak, increase gradually, watch plant response.

## Changing Your Reservoir

Nutrients deplete unevenly. Plants take what they need, leaving imbalances. Even if EC stays constant, the nutrient ratio changes.

Full system change: Every 1-2 weeks for recirculating systems. Empty, rinse, refill with fresh solution.

Kratky systems: Usually one fill per grow cycle for lettuce and herbs. Larger plants may need careful topping up.

Top-up practice: Between changes, add plain water (not more nutrients) to maintain level. Why? Plants drink more water than nutrients in hot weather, concentrating the solution. Adding more nutrients worsens this.

## What to Avoid

Overfeeding: The most common beginner mistake. More nutrients doesn't mean more growth. Start at half strength and increase only if plants look pale or slow.

Mixing brands: Different brands use different formulations. Mixing can cause imbalances or precipitation. Pick one brand and stick with it.

Using soil fertiliser: Miracle-Gro and similar aren't formulated for hydroponics. They lack micronutrients and can leave residues. Use proper hydroponic nutrients.

Ignoring water quality: Hard water adds calcium and magnesium. This might mean you need less cal-mag supplement. Know your water.

Never changing solution: Even if EC looks fine, nutrient ratios drift. Regular changes prevent subtle deficiencies.

## Troubleshooting Nutrient Problems

Brown, crispy leaf tips: Nutrient burn. Solution too strong. Dilute with plain water, reduce concentration next mix.

Yellow older leaves: Usually nitrogen deficiency or pH lockout. Check pH first. If pH is fine, increase nitrogen.

Purple stems or undersides: Phosphorus deficiency or cold temperatures. Check temps. If warm enough, increase phosphorus.

Yellow between veins (interveinal chlorosis): Magnesium or iron deficiency. Often pH-related. Check pH first.

Slow growth with dark green leaves: Possibly too much nitrogen or root problems. Check roots for rot.

## Our Recommendations

**Best for complete beginners: Formulex** One bottle does everything. No measuring ratios, no matching A to B. Add 5ml per litre, adjust pH, done. Perfect for Kratky herbs. *(Price when reviewed: ~£12 | Check price)*

**Best for most growers: General Hydroponics Flora Series** Three-part system allows customisation for different crops. Extensive feeding charts available online. NASA uses it. The global standard. *(Price when reviewed: ~£35 | Check price)*

**Best for recirculating systems: CANNA Aqua** Specifically formulated for NFT and DWC. Very clean formula minimises buildup. Dutch quality. *(Price when reviewed: ~£30 | Check price)*

Get an EC meter: Around £15-25 removes guesswork. The single most useful diagnostic tool after a pH meter.

Take our quiz for nutrient recommendations matched to your specific crops and system type.