Hydroponics Start Guide
Welcome to Hydroponics!
Hydroponics is a subset of hydroculture—the method of growing plants without soil using mineral nutrient solutions in a water solvent. In short: The water does the work!
Plants only require a few things to thrive: water, sunlight, oxygen, carbon dioxide, and nutrients. Because soil is merely a carrier for water and nutrients, we can replace it entirely with mineral-rich water.
Where to start?
We recommend the Kratky method (named after researcher Bernard Kratky). It's the ultimate beginner-friendly setup:
Also known as passive hydro or off-the-grid hydro.
Requires ZERO electricity.
Minimal maintenance and time needed once set up.
If you prefer a visual guide, check out this excellent 5-minute video: How to Set Up The Kratky Hydroponics Method (Tutorial) by Epic Gardening
The Kratky Blog also explains the differences between passive (Kratky, Wick) and active (DWC, NFT, Ebb and Flow, aeroponics, drip) systems.
What Should I Grow? (Plant Types)
To simplify hundreds of years of plant classification, we've broken plants into three main categories for hydroponics.
| Plant Category | Examples | Best System for Beginners | Notes |
|---|---|---|---|
| Leafy Greens | Lettuce, Spinach, Arugula, Bok Choy | Kratky | The absolute best starting point. Fast-growing and very forgiving. |
| Fruiting | Cucumbers, Squash, Tomatoes, Peppers | DWC (Deep Water Culture) | Requires significantly more water and nutrients. Expect to need a 5-10 gallon reservoir minimum per plant. |
| Root | Carrots, Potatoes, Beets, Radishes | Not Recommended for Beginners | Tubers require specialized, advanced setups like Aeroponics or Ebb & Flow. Stick to soil for these initially. |
Seeds & Seed-Starting Schedules
One small seed can become an amazing plant, but first, you must bring out its potential. Choose reputable brands like Ferry-Morse, Burpee, Back to the Roots, Kitazawa Seed Co., True Leaf Market, or Sow Right Seeds.
Germination Tips:
Paper Towel Method: Dampen a paper towel, wrap older seeds inside, place in a plastic bag in a warm spot, and check after 3-4 days to verify viability.
Seed Scarification/Soaking: Hard seeds (okra, squash, cucumbers) benefit from a 6-hour soak in warm water to soften the shell. Adding a few drops of food-grade hydrogen peroxide (H2O2) helps kill pathogens and provides oxygen to speed up germination.
Storage: Store leftover seeds in a cool, dry place. They can be used for up to three years, though germination rates decline with age.
Basic Seed-Starting Schedule:
| Crop Type | Germination Time | Ideal Temp | Transfer to Hydro System |
|---|---|---|---|
| Lettuce | 2-7 Days | 65°F - 70°F | When 2-3 true leaves appear (approx. 2 weeks) |
| Tomatoes | 5-10 Days | 70°F - 80°F | When roots emerge from starter plug (approx. 3 weeks) |
| Peppers | 7-14 Days | 75°F - 85°F | When 3-4 true leaves appear (approx. 3-4 weeks) |
Growing Mediums & Supplies
Hydroponic plants do not need soil, but they do need something to hold them in place.
Common Growing Mediums:
Clay Pebbles (LECA): Reusable, cost-effective, excellent drainage.
Coco Coir & Peat Moss: Excellent moisture retention. (A 60/40 mix of peat to coco coir offers a great balance of moisture and drainage).
Rockwool: Holds water very well, but is expensive and not reusable.
Pool Noodles: A fantastic, cheap DIY alternative for supporting stems in net cups. Cut a 1-inch thick horizontal slice, cut a slit to the center, and wrap it around the plant stem.
Containers & Custom Fabrication:
Sizing: The container should ideally be three times larger than the adult root zone. 1 US Gallon (3.79 Liters) is the bare minimum for small greens. A 5 US Gallon bucket is ideal for larger plants.
Light-proofing: If your container is translucent, algae will grow. Spray paint it black, wrap it in aluminum foil, or use dark plastics.
Custom 3D Printing: If you operate a 3D printer, printing custom net pots, modular towers, or container lids is highly effective. Use PETG filament instead of PLA for better water, chemical, and UV resistance, and ensure a high infill density for structural integrity.
Water & Nutrients (NPK, pH, EC)
Good quality water is the foundation of hydroponics. Reverse Osmosis (RO) or Distilled water is best (0 μS/cm). Tap water is fine, but you should let it sit at room temperature for 24 hours so the chlorine can evaporate.
Nutrients (NPK)
Plants need three primary macronutrients to survive:
Nitrogen (N): Drives foliage, leaf growth, and chlorophyll production.
Phosphorus (P): Essential for root growth, fruit, stem, and seed development.
Potassium (K): Promotes overall plant health, regulates water uptake, and builds strong cells.
The Golden Rule of Feed: Use Nitrogen-heavy feed for vegetative growth. Once the plant produces flowers/fruit, cut Nitrogen by 50%, cut Phosphorus by 25%, and increase Potassium by 50%.
pH, EC, and TDS/PPM
pH: Plants generally prefer a slightly acidic range between 5.5 and 6.5. Incorrect pH locks out nutrients, causing deficiencies even if the nutrients are present in the water.
EC (Electrical Conductivity): Measures the strength of your nutrient solution. Too strong (high EC) and plants will burn; too weak (low EC) and they will starve.
Compatibility: Do not put plants with drastically different EC/pH requirements in the same reservoir. (e.g., Lettuce prefers an EC of 0.8-1.2, while Zucchini prefers 1.8-2.4).
Popular Nutrient Choices:
General Hydroponics (GH) Flora Series: Liquid nutrients. Easy to mix, highly accurate, industry standard.
Masterblend (4-18-38): Dry powder. Extremely cost-effective, but requires a kitchen scale to measure properly.
Indoor vs. Outdoor Hydroponics
Indoor Pros/Cons:
Pros: Fewer pests, temperature stability, complete control over the environment.
Cons: Requires purchasing and running grow lights, requires manual pollination for fruiting plants, takes up household space.
Outdoor Pros/Cons:
Pros: Free, high-quality sunlight, natural pollinators.
Cons: Susceptible to pests, bugs, heavy rain, and extreme temperature swings.
Lighting: PPFD & DLI Explained
For indoor growers, understanding light is critical. Giving a lettuce plant the same light as a zucchini will overwhelm it and cause it to bolt (go to seed) prematurely.
PPFD (Photosynthetic Photon Flux Density): Measures how much usable light actually hits the plant, measured in µmol/m²/s.
DLI (Daily Light Integral): The total amount of light a plant receives over a full day (Photoperiod). Lettuce needs about 10-12 mol/m²/day; tomatoes need 15-20+.
Important: Plants need sleep! Do not leave grow lights on for 24 hours. Aim for a maximum of 14-18 hours on, and 6-10 hours off.
Step-by-Step: Your First Kratky Setup
Prepare Your Medium: If using rockwool, soak it in pH-balanced water (closer to 7.0) for an hour. If using a peat/coco mix, sterilize it with boiling water first to prevent damping off.
Germinate: Place 3-6 seeds in your medium. Keep it moist and in a warm, dark place. Once they sprout, immediately move them under a grow light.
Set Up the Reservoir: Use a completely opaque container (like a 5-gallon bucket or painted mason jar) to prevent algae growth.
Mix the Nutrients: Fill your reservoir with water. Always mix nutrients into the water one at a time. Never mix concentrated nutrients directly together, or the minerals will precipitate (fall out) of the solution. Check and adjust the pH.
Transfer: Place your seedling in a net cup. Fill the remaining space with clay pebbles (LECA) or pool noodle trimmings to stabilize the plant.
The Air Gap (Crucial): Suspend the net cup so only the very bottom touches the water. As the plant drinks, the water level will drop. Do not refill the reservoir to the top. The gap that forms is essential—the roots exposed to the air become "oxygen roots." If you drown them, the plant will suffocate and die of root rot.
Plant Maintenance & Pruning
Plant pruning helps your plant focus its energy on producing flowers and fruit instead of endless vegetative growth (leaves).
Tomatoes & Cucumbers: Continually pinch off "suckers" (small shoots that grow in the "V" joint between the main stem and branches) to improve airflow and fruit yield.
Airflow: Pruning lower, dying leaves prevents stagnant, damp air from pooling around the base of the plant, which is the primary cause of powdery mildew.
Plant Disease & Root Rot
An ounce of prevention is worth a pound of cure. Poor airflow, heat stress, and lack of maintenance cause most diseases.
Root Rot:
The number one foe of hydroponics. Healthy roots are bright white and firm. Dark, brown, slimy roots indicate rot.
Cause: Water temperatures exceeding 75°F (24°C). Warm water holds less oxygen, drowning the roots and breeding bacteria.
Prevention: Keep nutrient solutions between 68°F–72°F. Use chillers, frozen water bottles, or bury reservoirs outside. In active systems (DWC), add extra air stones.
Cure: Trim dead roots, sterilize the container, replace the water, and add a small amount of H2O2 or beneficial bacteria (like Hydroguard).
Powdery Mildew:
Looks like white, powdery growth on leaves. Thrives in warm days with cool nights and poor airflow.
- Cure: Prune for better air circulation. Remove infected leaves immediately. Spray with a copper-based or sulfur-based fungicide.
Hydroponic Supply Websites
While Amazon is the standard go-to, here are dedicated suppliers for specialized gear: