Home growing: windowsill, balcony and terrace · Guides

Growing guides · Home growing: windowsill, balcony and terrace

Hydroponic systems

At home, deep water culture (DWC) is the simplest starting point. More complex systems such as NFT, ebb and flow and drip rely on pumps: if power fails, roots can dry out quickly. Every figure comes from university extension sources; nothing is invented.

Rule: we never invent figures. If a source has no exact value, we say so.

DWC (bubbler) – deep water culture

A “bubbler” is usually a simple aerated deep water culture: plants sit in net pots in a lid and the roots hang into the nutrient solution, which an air pump and air stone oxygenate. University sources use the terms DWC or floating raft. [1][2]

How it works

  • Plants are suspended above a tank of water and the roots hang into the container, where they absorb water and nutrients. [1]
  • The most common support is a net pot with a substrate (for example clay pebbles, perlite, coir or rockwool). The net pot should only be partly submerged so roots can get oxygen. [1]
  • In a single container, an air stone is the most common aerator: tubing connects it to an external pump, and the porous stone releases tiny bubbles. [1]
  • The name “deep water” can be misleading: the water only needs to be a bit deeper than the roots. Missouri Extension’s common recommended depths are 4–12 inches (10–30 cm). [3]
  • In a passive DWC (the Kratky method), aeration comes from the air gap above the water. That is why the net pot is only partly submerged as seedlings grow, and developed roots are kept about one-third to one-half in the water. [1]

Pros and cons

  • According to UMN Extension, DWC is the simplest, least expensive and easiest system to maintain and expand for small-scale home use. [1]
  • Missouri Extension notes that DWC is more forgiving for beginners because plants will not immediately wilt if an aeration pump fails. Over time, though, it uses more water and fertiliser than NFT, and adjusting temperature, pH and dissolved oxygen can be more costly. [3]

Suitable plants

  • Leafy greens and herbs are commonly grown in DWC. UMN recommends lettuce, herbs and brassicas such as kale and mustards year-round; in summer also strawberries, tomatoes, cucumbers and peppers, though the extra heat and light needed indoors is cost-prohibitive for most gardeners. [1][3]

What you need and how to maintain it

  • Basics: a clean, food-safe container (for example a 5-gallon bucket or storage bin), a lid or polystyrene board, net pots, substrate, nutrients and a light source. For a single container, an air pump and air stone. [1][2]
  • Keep about half of the roots in the water. Top up with nutrient solution, not plain water. For lettuce harvested in 6–7 weeks, UMN says a full change is not always needed; for a long-season crop such as tomato, change the solution completely once or twice during the season. [1]
  • UNH Extension says aeration is critical in raft systems to prevent root damage. Use water that is safe to drink; for home hydroponics a pH between 5.5 and 7.0 is fine. [2]

Common beginner pitfalls

  • Roots fully underwater: UMN warns that too much water stops roots getting oxygen and can lead to root rot. Roots should always touch the water, but should not be fully immersed. [1]
  • Light reaching the nutrient solution: use opaque materials and a lid on the reservoir to reduce algae. [1]
  • Not testing pH. UMN recommends testing the tap water and again after adding fertiliser; plants do best at pH 5.4–7. In a small system, testing every few weeks is often enough. [1]

RDWC – recirculating deep water culture

How it works

  • When you have many containers, UMN says a recirculating DWC is more common: containers are connected with tubing, and a larger pump circulates oxygenated water between the containers and a reservoir. [1]

Pros and cons

  • You can balance pH and nutrients in one reservoir instead of managing each container separately. UMN notes that prefabricated RDWC systems tend to be costly for hobby growers; you can also build your own. [1]
  • A recirculating system depends on a pump. UMN warns that in more complex systems a malfunction or power cut can leave plants without water, and they can dry out quickly. [1]

Suitable plants

  • It suits the same crops as a single DWC, but across several containers: leafy greens and herbs, and in summer also fruiting plants if light and heat are sufficient. [1][3]

What you need and how to maintain it

  • You need a circulation pump, connecting tubing, a shared reservoir and aeration. Maintenance focuses on pH and nutrients in that one reservoir, and on keeping the pump and tubing working. [1]

Common beginner pitfalls

  • A pump or tubing fault going unnoticed. UMN advises checking that plumbing is working; wilted plants may be the first sign that something is wrong. [1]

NFT – nutrient film technique

How it works

  • Plant roots extend into a trough or pipe where a shallow nutrient solution flows continuously over the roots and returns to the reservoir. [3][1]
  • Troughs must sit at a 1–2 percent slope (Missouri: 0.12–0.24 inch per foot). Aeration is not needed because the solution is so shallow that roots are exposed to air and oxygen dissolves easily. [3]
  • Illinois Extension notes that nutrients can flow over the roots for up to 24 hours a day. [4]

Pros and cons

  • NFT uses less water and fertiliser than DWC, and Missouri Extension says adjusting solution pH and temperature is easier than in many other systems. [3]
  • If the pump fails or lines clog, plants may wilt immediately. Illinois describes NFT as very unforgiving, because there is no growing medium to hold moisture. [3][4]

Suitable plants

  • Lettuce, herbs and strawberries are commonly grown in NFT according to Missouri Extension. UMN also lists arugula, kale, spinach, Swiss chard and microgreens as suitable NFT crops. [3][1]

What you need and how to maintain it

  • Parts: a reservoir, channels, supply and drain lines, and a circulation pump. UMN advises checking plumbing, pests and disease, the reservoir level (if it falls below the pump, the pump can be damaged), and pH and electrical conductivity (EC) weekly. [1]
  • Change the nutrient solution after each crop, or during production if growth is slow. For crop-specific pH and EC, UMN refers readers to Oklahoma State’s Electrical Conductivity and pH Guide for Hydroponics. [1][5]

Common beginner pitfalls

  • Clogs and leaks: plant debris, algae or precipitated nutrients can block narrow tubing; hard water can leave mineral deposits. UMN advises reducing light to the reservoir and using the proper nutrient level to limit algae. [1][3]
  • UMN says rainwater is not a safe source for leafy greens because it can harbour bacteria and parasites. Softened water can start the system with excess salt, and hard water may be high in calcium and magnesium. [1]

Ebb and flow

How it works

  • Plants grow in a tray with substrate. A pump lifts nutrient solution from a reservoir into the tray, then it slowly drains back through the porous substrate or a drain line. [1]
  • Illinois Extension says the submersible pump should remain on for a 20–30 minute flood cycle. Once the water has reached a set level, an overflow pipe lets the solution drain back to the reservoir. [4]

Pros and cons

  • Illinois describes the system as low-maintenance and highly effective. The substrate holds moisture between floods, unlike NFT. Units can be bought ready-made or built from buckets and plumbing supplies. [4][1]
  • As with other pumped systems, a power cut stops watering (Illinois: no power = no water). [4]

Suitable plants

  • Missouri Extension classes ebb and flow as a media-based system. Larger-rooted or fruiting plants often suit media watering better than a thin NFT film; the sources do not give a separate crop list just for this system. [3]
  • Illinois notes that expanded clay pellets are great for ebb and flow systems. [4]

What you need and how to maintain it

  • You need a reservoir, a submersible pump, a tray with substrate, and an overflow or return line. A timer runs the pump for the flood cycle. Illinois says pH and EC must be tested regularly, and the nutrient solution replaced every 2–3 weeks. [4][1]

Common beginner pitfalls

  • Missing a timer or overflow, so the tray can flood or dry out. Illinois emphasises an overflow pipe and a set flood cycle. [4]

Drip systems

How it works

  • Nutrient solution is delivered through a hose and emitters to the base of each plant in a substrate. Some systems return excess solution to the reservoir; others do not. [1]
  • Missouri describes drip irrigation as the way nutrient solution is delivered to each container (for example a Dutch bucket). The solution passes through the media and drains back to a reservoir in a closed system. [3]

Pros and cons

  • It suits larger fruiting plants and many media (coir, rockwool, perlite, expanded clay). Missouri Extension notes that media containing organic matter need more intensive pH management. [3]
  • Lines can leak or clog, and a pump failure leaves plants without water, as in other active systems. [1][4]

Suitable plants

  • Missouri Extension says a Dutch-bucket drip system is ideal for tomatoes, cucumbers and other vining or fruiting crops. UMN mentions tomatoes and strawberries in coir bags in high tunnels. [3][1]

What you need and how to maintain it

  • You need a reservoir, pump, tubing and emitters, plus media in containers or bags. Check emitters for clogs. Irrigation frequency depends on the media: the sources do not give one schedule for all media. [3][1]

Common beginner pitfalls

  • Clogged emitters going unnoticed, so a single plant dries out. Missouri advises monitoring drip lines for leaks and clogs. [3]

Open the home-growing tools

These are general guidelines. Always check the variety, seed packet or fertiliser instructions and current regulations.

Sources

  1. University of Minnesota Extension: Small-scale hydroponics
  2. University of New Hampshire Extension: Hydroponics at Home (August 2023)
  3. University of Missouri Extension G6986: Controlled Environment Agriculture: Hydroponic Farming (July 2024)
  4. University of Illinois Extension (C. Hart): Home Hydroponics (PDF handout)
  5. Oklahoma State University Extension: Electrical Conductivity and pH Guide for Hydroponics