Indoor gardening: what is a passive hydroponic system?

What is a passive hydroponic system?

A The passive hydroponic system is the easiest and least troublesome way to grow your indoor plants. It uses some type of technique to hang a plant and supply water to the reservoir where the roots are hanging. The water supplied is supplemented with nutrient solutions which contain all the necessary minerals, including macronutrients and micronutrients, to help plants reach their growth potential. It also helps determine how much nutrient solution the plants are getting and how long it takes to fill the water reservoir.

Passive hydroponic system for indoor plants

In the world of hydroponics, there are two types of passive hydroponics which are soilless and soilless. The soil type is the soil commonly used in gardening, while the soilless type which is also classified as a “soil” in hydroponics is the use of growing media such as Leca as soilless soil.

Why is Leca perfect for indoor gardening?

LECA or Hydroton clay pebbles
LECA or Hydroton clay pebbles

LECA, also known as Hydroton Pebbles or Clay is a growing medium used for above-ground potting soil to grow your plants. It’s an acronym that stands for Lightweight Expanded Clay Aggregate, made up of fired clay balls that absorb and expand when soaked in water. Leca acts as a sponge-like medium that absorbs water to keep your plants hydrated. However, although Leca is used as a soil substitute, it does not contain the nutrients your plants need, and you will need to add the nutrients to the water where you will be soaking the Leca.

Since Leca is a different growing medium, normal plant food is not recommended to provide the nutrients your plants need; instead, you have to buy a special hydroponic fertilizer.

Now the question is, why should you switch to Leca? Even though it doesn’t contain the nutrients your plants need, there are many benefits to using Leca. The advantages are:

  • It is easier to keep your plants hydrated by soaking Leca in water with a nutrient solution.
  • The risk of catching parasites is reduced because Leca does not contain living organisms that parasites could feed on.
  • The risk of root rot is less in Leca, as it only absorbs water and overwatering is avoided.
  • It is easier to control your plants daily or twice a month using Leca.
  • Leca is a reusable growing medium that you can reuse after cleaning it thoroughly.

Buy LECA on Shopee

Semi-hydroponic methods for houseplants

There are six basic methods in hydroponics, and each method has a different layout. These methods are:


Self Watering Transparent Flower Pot
Self Watering Transparent Flower Pot

This is the simplest and cheapest system, in which one or more wicks are used to absorb the nutrient solution from the reservoir and deliver it to a sterile medium. This system is recommended for small installations and beginners because it does not require pumps or drainage systems. There are also self-watering pots that use this technology.

Ebb and flow

This system uses a timed pump that periodically floods the container with nutrient solution, then the drained solution returns to the water reservoir. The flood system works well for the greenhouse garden, which can keep the roots moist.


The most complicated system is the Drip System. It uses hoses and drip lines to deliver the nutrient solution to plants individually and is suitable for larger plants.

Nutrient film technique

NFT is designed for a large greenhouse setup. In this system, plants are hung in a plastic basket and placed in trays. The nutrient solution is delivered through tubes to hydrate the roots of the plant, then the drained solution returns to the reservoir.

Water culture

This system is best suited for fast-growing plants like lettuce, where a polystyrene tray or other floating material is placed over the reservoir.


Aeroponics is the most expensive system, where the roots of the plant are suspended in a less dense growing medium and then water is sprayed over the suspended roots to keep the plant hydrated and provide necessary nutrients.

The references

  • Hydroponics, Albopepper Clayton, (2017),
  • What is a passive hydroponic system, Garden Culture Magazine (2012),
  • Passive hydroponics and hydroponic systems in containers, garden and greenhouse
    Tilley, Indoor Hydroponic Gardening, Gardening Know-How
  • What is Leca and why is it useful for plants, Plant Care For Beginners
  • The Pros and Cons of Using Leca to Grow Your Plants, Plant Care For Beginners
  • Indoor gardening techniques I love to know
    Willis, (2018),
  • Indoor growing methods and techniques, indoor farm life

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