The Best Gravel for Hydroponics

Written by tracy morris
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The Best Gravel for Hydroponics
Some forms of hydroponic systems call for a plant to grow in a soil-free substrate such as gravel. (Jupiterimages/BananaStock/Getty Images)

Hydroponic systems involve growing plants without soil. Although some systems support plants from above and leave the roots to float in a nutrient solution, others support the plant from the roots using a soil-free substrate. This substrate may consist of any number of gravel products. The substrate must be loose enough to allow the roots and hydroponic nutrients to flow through it easily.

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Pea gravel

Pea gravel is made up of rounded stones smaller than 1 inch in size. These stones fit together tightly, yet have enough space between each stone that liquid such as the hydroponic nutrient solution can pass through them easily. Pea gravel may be used in building projects such as driveways as well as in the bottom of aquariums. Pea gravel is heavier than substrates such as peat moss or even perlite. This can be helpful for growing top-heavy plants such as tomatoes, which may otherwise tip over.


Pumice is a volcanic rock similar to perlite. Pumice is denser than perlite and can help to weigh down a container of hydroponic nutrients similarly to pea gravel. Pumice is formed when volcanic rock bubbles like carbonated soda in the presence of volcanic gasses and then cools. Pumice may initially float on water, but will sink once it becomes saturated.

Lag Gravel

Lag gravel is coarse gravel that is collected from river beds after all fine, smooth gravel has been removed or washed away. Lag gravel may also be seen on a desert floor after wind has carried away all smaller sediments. The gravel's irregular angles prevents it from fitting tightly together and leaves plenty of space between the individual stones for water as well as root development.

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