Hydroponic and Aquaponic Growing Media:
You have landed on this page for one of two reasons:
1) You already know you want to use lava rock for your hydroponic or aquaponic growing media,
2) You wanted more information about whether lava rock would work for your particular hydroponic or aquaponic project.
Whichever the case, we have gathered information to answer your questions. Check out whichever section below applies to you.
Where to Find Lava Rock
Lava rock is not nearly as common as some other growing media supplies, but it can be found. A good first stop would be your local hardware store or home improvement store. They may not carry lava rock as regular stock, but they can probably special order it in small quantities. They may need to order at least a pallet's worth as a minimum order, so be sure to check how much lava rock you'll need, and that will help determine whether your order meets the minimum special order requirements.
A second local source would be landscaping suppliers or topsoil suppliers. They may have bagged lava rock but will more likely have it in bulk, priced either by volume or weight. They may be able to offer lower prices than the hardware stores or home improvement stores since they already carry it in bulk. But check prices on both to see who offers the best deal.
A third option is to try online hydroponic suppliers. Some will carry lava rock specifically for planting purposes. Or they may know of local or regional suppliers. Lava rock doesn't ship as well as some other soil amendments due to the weight and bulk, but it's worth a try to see what they might have.
Advantages and Disadvantages of Lava Rock as Growing Media
One intriguing growing media that we have not yet worked with, but we know others who have, is the use of small lava rock. Lava rock is a lightweight, natural, pH neutral material that is much more porous than any other type of rock. The larger pieces are much easier to use and dramatically lighter than either gravel or sand, yet is heavier than perlite and permiculite. It has good water retention capacity due to all its little pockets and irregular stone faces, which all form tiny little reservoirs that roots can draw from between irrigation cycles.
Lava rock can be dusty when you first get it, but it rinses clean fairly quickly. The cost is higher than gravel and sand, and depending on your location may be more costly than perlite and vermiculite, but it is often cheaper than rockwool or hydroton.
As we continue with our hydroponic and aquaponic work we will be experimenting with this substance. We will report on our findings after some experience.