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Full Guide To Using Lava Rocks in Your Hydroponic System

Full Guide To Using Lava Rocks in Your Hydroponic System

Are you considering replacing your current hydroponic growing medium with lava rocks? Unsure of its effectiveness? Look no further, as this post has got you covered!

Lava rocks may be used for hydroponics. In fact, thanks to their lightweight and porous nature, they are highly effective for such use. But, before you add them to your system, you should rinse and sterilize them. Also, take into consideration that in outside hydroponic systems, the sun may heat them up and cause the nutrient solution in the system to raise as well.

Read on below and discover everything you need to know about using lava rocks in your hydroponic system.

Using Lava Rocks for Hydroponics

Lava rocks are one of the most popular growing mediums for hydroponics, aside from clay pellets, river rock, and Rockwool. Using them is simple, which we break down for you in the following sections.

How To Use Lava Rocks for Hydroponic Systems

Lava rocks are a great addition to your growing systems, but first, you must select the right ones for the job.

A few of the main considerations to take into account while selecting the best lava rocks for your hydroponic system include:

  • Size. The size and surface area of the lava rock you choose for your grow sites is a crucial factor as it goes a long way in determining which types of plants they’ll support.
  • Quality. As with most growing mediums, all lava rocks aren’t of the same quality. Lower quality rocks will need replacing much sooner than high-quality rocks.
  • pH. Most lava rocks are pH neutral, but this isn’t always the case. Make sure you check this seemingly small factor before adding them into your system and disturbing the pH balance.
  • Drainage. The porousness of the rocks determines how well their drainage capability is.

Once you’ve picked up the lava rocks you’ll add to your system, follow these simple steps to use them:

  1. Place the rocks in the sink, or a bucket of water, and rinse them well.
  2. Repeat until the water draining from them is clear.
  3. Soaking them overnight isn’t necessary like with LECA, so after they are rinsed you may add them to your grow sites or growing tanks.
  4. Place transplants directly into the lava rock in your hydroponics system as you would with any other growing medium.

Benefits of Using Lava Rocks

There are a number of benefits that come with using lava rocks in hydroponic growing systems:

  • Lava rocks are one of the most lightweight growing mediums around thanks to their air pockets in them. 
  • Compared to other growing mediums commonly used in hydroponics, lava rock is extremely low maintenance.
  • Lava rock is available in several different colors, including grey, black, brown, red, and other variations.
  • Due to their highly porous nature, lava rocks have great drain ability, making them less likely to grow fungus or bacteria.

Potential Drawbacks of Using Lava Rocks

The main potential disadvantages of using lava rocks for hydroponics are:

  • Lava rock is extremely light and may be easily disturbed if you bump into your grow sites
  • The rocks are more expensive to replace than other popular types of growing mediums. 
  • There is also the slight chance that if you have a spill they could cause damage to equipment like tarps, grow tents, or even your hands or feet.

Additional Growing Mediums for Hydroponics To Consider

Many suitable growing mediums for hydroponics exist, here are some of the best ones to consider for your system:

  • Pebbles
  • Lightweight Expanded Clay Pellets (LECA)
  • Coco Coir
  • Pea Gravel
  • Perlite
  • Hemp Fiber
  • Rockwool
  • Sand
  • Foam
  • Other inert mediums like river rocks

Related Question:

What Kind of Rocks Can I Use for Hydroponics?

There are several types of rocks that you can use for hydroponics other than lava rocks. River rock, pea gravel, and other small stones work just fine. That said, keep in mind that light may heat up rocks which, in turn, raises the temp of the nutrient solution in your hydroponic system.


Lava rocks may be just what the doctor ordered for your hydroponic system. They are lighter than other mediums, have excellent drainage, and come in multiple colors. 

That said, they may cost a bit more than other growing mediums like LECA or pea gravel. Also, keep in mind that they still require some cleaning and sterilizing from time to time.