Can You Use Lava Rocks For Hydroponics? (FULLY EXPLAINED)

Hydroponics is a soilless gardening method that requires an inert growing medium, like LECA, Coco coir, or lava rocks.

Can you use lava rocks for hydroponics?

Lava rocks are a common choice for a stand-alone hydroponic growing medium because they are extremely porous, organic, pH neutral, retain water, are easy to handle, and are readily available. Most importantly, lava rocks for hydroponics also come in various shapes, sizes, weights, and colors.

Read on below for the full explanation of using lava rocks for hydroponics!

Why Use Lava Rocks for Hydroponics?

Lava rocks are one of the best inert growing mediums to use for hydroponics. Due to their highly porous nature, fungus, algae, and bacteria are much less likely to grow on the surface of lava rocks.

Lava rocks are also weightier than some popular hydroponic growing mediums such as coco coir or peat. That means it’s a better anchor for medium to large hydroponic plants than other growing mediums.

Further, lava rocks are one of the only types of hydroponic growing medium that you can purchase in several different colors. Lava rocks can also be used as an ingredient for high-end succulent and cacti growing medium mixes.

Aside from being more aesthetically pleasing, you can also use lava rocks to make color-coded grow sites and keep track of what you’re growing more easily.

In addition, lava rocks are great to have on hand if you have multiple hydroponic grow sites, fish tanks, or aquaponic growing systems. Lava rocks also work well for mixing into bonsai soil mixes.

Lava rocks are also known for removing nitrates from the water, which makes them even more of a diverse growing medium for hydroponics and aquaponic systems.

One last note-worthy reason to use lava rocks for hydroponics is that they are readily available and practically last forever. Lava rocks don’t really age like other growing mediums.

Drawbacks of Lava Rocks for Hydroponics

As impressive of a hydroponic growing medium that lava rocks are, generally speaking, there are of course a few minor drawbacks.

The most significant downside to using lava rocks for hydroponics is that they are inert, meaning they provide zero nutrional value to your hydroponic system. 

The catch is that hydroponic growing systems typically require, or certainly work out better with, an inert growing medium. 

Hydroponic systems require an extremely well-balanced pH level, and growing mediums that do provide nutrients throw the carefully measured balance out of whack.

Another semi-negative point is that lava rocks are somewhat expensive. That said, for the most part, all hydroponic growing mediums are a bit pricey.

The upside to the price of lava rocks is that they pretty much last forever, unlike other growing mediums that quickly degrade.

What Types of Lava Rocks Should I Use for Hydroponics?

What Types of Lava Rocks Should I Use for Hydroponics?

The most beneficial type of lava rock to use in hydroponic growing systems is volcanic basalt.

In fact, the coarse basalt lava rocks are often so beneficial that they are actually used as a rooting agent for hydroponic plants and cuttings.

However, there are numerous sizes and shapes of lava rocks for hydroponics, all of which work well with various hydroponic and aquaponic systems.

Likewise, lava rocks come in a wide variety of colors including blue, red, green, yellow, purple, orange, teal, and more. 

The most common color for hydroponic lava rocks, however, is gray followed by black and then white.

How to Use Lava Rocks for Hydroponics Properly?

Using lava rocks for hydroponics is a straightforward method. In fact, lava rocks are much easier to handle than most types of hydroponic growing mediums.

Lava rocks must be rinsed, thoroughly, and preferably washed with lightly soapy water and rinsed again before being used in your hydroponic growing system.

After your lava rocks are cleaned and sterilized, it’s time to add them to the hydroponic growing system’s individual grow sites one by one.

The easiest way to fill the sites is by removing them, preparing plants to place in them, and then filling them up with a handful of lava rocks, the plant’s roots, and then more lava rocks. 

Stop adding the growing medium to the grow sites only when you’ve completely covered the roots and filled the site up to the fill line.

If the sites are stationary, take the container of lava rocks with you around it and place several handfuls of lava rocks in each one.

Alternate Rock Options for Hydroponics

Alternate Rock Options for Hydroponics

If you find that lava rocks just don’t seem to be the best growing medium for your hydroponic growing system, fret not. 

There are many many more options out there in regards to great growing mediums that are easy to use for hydroponics.

A few of the most common alternative rock options for hydroponics include:

  • LECA. Lightweight clay aggregate, or LECA for short, is a stone-like ball of hardened clay that has incredibly high water retention rates.
  • Fishtank Pebbles. Teeny tiny little pebbles of brightly painted colors that typically go in the bottom of fish tanks can be used for hydroponic growing medium in a pinch.
  • Pea Gravel. Small pieces of gravel are an excellent growing medium for larger hydroponic plants that constantly have their roots exposed to water, such as in deep water culture (DWC) hydroponics.
  • River Rocks. River rocks are typically smooth and round rocks the size of coins or slightly bigger or smaller, and they work well as a filler or stand-alone growing medium for large and medium hydroponic grow sites.
  • Stones and Rocks. Other small stones and rocks can be used as filler in your hydroponic growing mediums, as well as for a stand-alone growing medium for medium to large plants.


Is Lava Rocks Toxic to Plants?

Lava rocks are not toxic to plants, animals, or humans (however, of course, we shouldn’t ingest them or allow our pets to do so). On the contrary, they are 100 percent organic though they offer zero nutrients.

Can you use lava rock in aquaponics?

Lava rocks are one of the best inert growing mediums there is for hydroponic growing systems, including aquaponic methods. That’s because it is wonderfully porous, retains lots of water, acts as an anchor for root systems of all sizes, and doesn’t affect the system’s pH or EC (electrical conductivity) levels.

Is The Lava Rock Use in Hydroponic Safe for Aquarium?

Using lava rocks for hydroponics is completely safe for aquariums. In fact, lava rocks are quite often used in such a manner. Further, they are more often used in aquariums, or for hydroponics, than they are for anything else for that matter. Even more, lava rocks are great for aquariums with fish because they lower the levels of nitrates in the water.

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Jordan Tyler Quinn Farkas

Jordan is a full-time writer, content creator, and indie author. When he isn't writing he's either spending time with his family or doing something outside. Jordan has a passion for DIY projects, home decor, gardening, camping, hiking, and primitive survival skills.

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