Lava Rocks For Aquaponics

black lava rocks for aquaponicsThe principle behind aquaponics is that the system will take care of its own needs. In return for monitoring the water and perhaps adding a few essential nutrients, you’ll have a gradual increase in fish stock and excellent plant growth. Lava rocks can help grow bacteria thus increasing the effectiveness of your aquaponics system.

The increase in fish quantities can be used to service more plant beds or you can simply consume them; depending on your tastes and what fish you have chosen to use.

However, the real trick to getting such good results is in taking the time to set your system up properly. You’re probably aware of the need to create nitrates in your water before you add the plants; this simply helps to ensure the whole system starts working straight away.

But, you may not have heard about using lava rocks for aquaponics; they can make an excellent grow media.

What Is Grow Media?

The fish are kept in their own tank and their water is pumped through to where you are growing your plants. The water needs to be available to the plants but also to circulate back to the fish; ensuring the cycle keeps going and both the fish and the plants are healthy.

It is possible to place boards on the water and position your plants so that their roots are constantly in the water. However, there are several risks with this method; including the plants being unable to absorb nutrients if there is any dirt in the water. The dirt will stick to the roots.

This is why most people who use aquaponics prefer to have growing media.

The growing media is simply the material that the plants are placed into. The water should be able to be accessed and absorbed through this media but the roots do not need to be in the water at all times.

Why Lava Rocks for Aquaponics?

red lava rocks for aquaponics

A rock base is ideal as the growing media for your aquaponics system for several reasons. However, before we continue it is essential to understand that you should use crushed lava rocks. They should be between 8mm and 16mm in size. This is small enough to make planting easy but large enough to ensure there is plenty of airflow around your plants. Air flow is essential for the healthy growth of your plants; their correct function will help to keep your fish alive and complete the cycle.

There are several benefits to using lava rock:

  • Light

Lava rock is very porous which makes it exceptionally light in comparison to most other rocks. The reason for this is that lava rock is actually not a rock at all; it is ‘frozen foam’; the air bubbles were frozen in place as the molten lava cools quickly. This makes it a great choice for your grow bed as it is easy to create a layer of lava rock just above the water base.

  • Easy To Locate

You’ll probably be able to find lava rock in a store near you; you may even find it in nature. Lava rock is surprisingly common and takes virtually no effort to collect and bring back to your plant beds.

It is also one of the cheapest materials you can get for your plant bed.

  • Porous

The fact that lava rock is either frozen foam or rock with plenty of air pockets reflects its ability to allow water through. This is because there are many tiny holes in the rock which have been created by the molten lava cooling so quickly.

Being porous means that the rock will allow your plants to get the nutrients and water they need without having the roots hanging in the water.

  • Doesn’t Affect pH Levels

Surprisingly lava rock is pH neutral. This means it won’t affect the pH of your set up. This is important as an incorrect pH will prevent your plants from growing properly and reduce the yield that you’ll get.

Getting the pH level right is important; that’s one of the reasons why lava rock is such a good choice.

Precautions When Using Lava Rock

Of course, there are a few things to be aware of when using lava rocks:

  • Dirt

The main issue that you should be concerned with when using lava rock is that it is a very dirty rock. It is essential to clean it thoroughly before you add it to your aquaponics system.

Dirt can quickly cause issues in your pipework and coat the roots of your plants; preventing them from absorbing nutrients.

You can’t wash lava rock too much!

  • Issues With Planting

It is possible that your plants will struggle to find their way through the lava rock to get the nutrients they need. Providing you use the right size lava rocks this shouldn’t be an issue but it is worth monitoring.

  • Hard on your hands

Ever tried scooping some lave rock with your hands? You will see that it’s not easy on your hands. It can make nasty scratches or wounds because it’s so sharp.

Other Options

If you are unable to get lava rock then you may wish to try one of these other growing media’s. Most people acknowledge that lava rock is the best option but these can be a good second choice:

  • Expanded clay

Expanded clay pebbles are even lighter than lava rocks. They also are able to resist mold and fungi. You’ll find it easy to dig through them and they will allow plenty of water flow. However, these are generally a very expensive option.

expanded clay pebbles

  • Coconut Coir

This is a good choice as it is pH neutral and very light. However, you should be aware that it is high in sodium. If you use it then you’ll need to choose a suitable product that will help you lower sodium levels in your tank.

Coconut Coir is also anti-microbial. This means it could kill the good bacteria in your tank; which is not good for your setup. This is a good choice when added to a gravel base and closely monitored.

coconut coir for aquaponics

  • River stone

River stone can be purchased at your local store and is generally round making it easy to root your plants. Providing you don’t go for anything too small it shouldn’t be an issue to the pipework in your system. However, river stone is heavy. If you want to keep your grow bed above the water you need to have strong support!

river stone for aquaponics

Lava rock may not be the first growing media you think of but it is certainly one that should be on your list; it is surprisingly effective at aiding plant growth without being too expensive.

Leave a Comment