Substrates

While not all hydroponic techniques need a soil-like substrate to place the seed in, all need some kind of support for the plants growing. The possibilities are therefore endless. It may be just a stretchable piece of rubber with a tiny hole in it to place the seed, a tiny cube made out of cocos, rock wool or sponges, or a bigger quantity of soil-mimicking substrates like sand, perlite, gravel, etc. – in this section you will get to know different possibilities how to place your plants in your hydroponic system as well as substrates' divers features. You could even improvise and come up with your own plant support! Just remember, that you want to use food-safe substances and that the plants' roots want nutrient rich water as well as air. And equally important, you want to make sure either to not provide living space for pests and diseases or to being able cleaning/replacing the substrate in case of infestation without damaging your plants.

Coco Coir

Material:

  • Coco husks (often pressed together and mixed with other substrates)

Water retention [5, 9]:

  • Very good water retention capacity

Aeration [5, 9]:

  • Good aeration

Additional Information [5, 9]:

  • Renewable, compostable material
  • If pressed into cubes, great for starting seedlings
  • Rinse/Wash with water before using

Chips

Material:

  • Coco, hemp or wood bark

Water retention [5, 9]:

  • Very good water retention capacity

Aeration [5, 9]:

  • Very good aeration

Additional Information [5, 9]:

  • Renewable, compostable material
  • Loose water quickly – frequent watering needed
  • Wash with water before using
  • If organic matter remained in the substrate, susceptible to pests

Expanded Caly Pellets

Material:

  • Expanded clay

Water retention [5, 9]:

  • Good water retention capacity

Aeration [5, 9]:

  • Very good aeration

Additional Information [5, 9]:

  • Inorganic, reusable material
  • Loose water quickly – frequent watering needed
  • Wash with water before using

Foam and Sponges

Material:

  • Polymeres (some of them compostable)

Water retention [5, 9]:

  • Good to very good water retention capacity

Aeration [5, 9]:

  • Very good aeration

Additional Information [5, 9]:

  • Organic, not reusable material
  • Some are compostable
  • Great for starting seedlings

Gravel

Material:

  • Gravel

Water retention [5, 9]:

  • Good water retention capacity

Aeration [5, 9]:

  • Very good aeration

Additional Information [5, 9]:

  • Natural, reusable material
  • Wash with water before using

Peat

Material:

  • Partially decayed plant matter

Water retention [5, 9]:

  • Very good water retention capacity

Aeration [5, 9]:

  • Good aeration

Additional Information [5, 9]:

  • Natural, nonrenewable material
  • Acidic pH around 4, hence good in combination with perlite or vermiculite 

Perlite

Material:

  • Aerated volcanic rock

Water retention [5, 9]:

  • Good water retention capacity

Aeration [5, 9]:

  • Very good aeration

Additional Information [5, 9]:

  • Natural, reusable material
  • Very light weight – getting washed away easily
  • Rinse with water before using

 


Rock wool

Material:

  • Rock wool / stone wool (often pressed to blocks or slabs)

Water retention [5, 9]:

  • Very good water retention capacity

Aeration [5, 9]:

  • Good aeration

Additional Information [5, 9]:

  • Inorganic, not compostable material
  • Great for starting seedlings
  • Soak in water before using

 


Sand

Material:

  • Sand

Water retention [5, 9]:

  • Good water retention capacity

Aeration [5, 9]:

  • Good aeration

Additional Information [5, 9]:

  • Natural, reusable material
  • Very heavy

Vermiculture

Material:

  • Heated mineral

Water retention [5, 9]:

  • Very good water retention capacity

Aeration [5, 9]:

  • Good aeration

Additional Information [5, 9]:

  • Inorganic, reusable
  • Expensive

Link to References