So you have decided it is time to grow your own organic food and provide your family with the best produce possible! (and maybe edible fish?) You have purchased your system and have set it up and are eager to add the herbs, vegetables, and fish. Prior to adding those vegetables, a decision has to be made about the type of media to use. Before purchasing, consider these things:
Is it the correct size?
Is it affordable?
Is it easy to work with?
Does it drain well?
Does it provide adequate surface area?
Will it drain well?
Will it affect the pH of your system?
Over the years, people have utilized many inert materials as grow media. Considering the above questions can help to avoid many pitfalls past aquaponic growers have experienced. You will want a material that is relatively neutral in pH, has plenty of surface area for bacteria to colonize, and one that drains well. It also needs to be cost-effective, easy to work with, and be light enough for your system. Hopefully, my experience with the following media can help you make the best decision for your system. The following are the four most popular types:
Pro: Gravel is readily available, and very inexpensive.
Con: Two most important disadvantages of gravel is it’s weight, and its unpredictable mineral content. Gravel is heavy. Most aquaponic systems require a minimum 10″ of depth to effectively produce vegetables . Dependent on the size of your system, this can equate to a considerable weight. The unpredictable mineral content raises concern due to not knowing what minerals will be introduced into your system over time. The most common mineral to leach is limestone, which will drive a pH of a system very high. Consistent, predictable, and as close to a neutral pH of 7.0 is desired. Anything other than that causes great distress to plants and fish.
Pro: An alternative to gravel, AquaRocks is designed specifically as an aquaponic grow media. It has a neutral pH, is significantly lighter than gravel, and has a plenty of surface are for nitrifying bacteria to grow.
Con: Compared to gravel, it is pricey. Utilizing this product for larger system builds, one must consider its cost effectiveness and whether the pro outweighs the con. It can also be a little rough on bare hands. Each system is unique and for some the AquaRocks’ performance makes it well worth the cost.
Expanded Clay Pebble:
Pro: Clay pebbles are the most commonly used media for aquaponic and hydroponic growers. It is lightweight, easy to work with, has a neutral pH, plenty of surface area, and is reusable. It drains well, and provides plenty of aeration. If you are using composting worms (highly recommended), the relatively smooth surface is easy on your worms.
Con: Like AquaRocks, clay pebble can be a little pricey for the larger aquaponic systems. Dependent on the manufacturer, you will also want to pay attention to size. Some brands have smaller pebbles that will often escape through gravel guards, etc. and get into your pump. (not good) Another concern is in the deeper beds (10″ to 12″), clay pebbles have a tendency to float. This can be very troublesome in an aquaponic or hydroponic system. The constant movement can cause disruption of plant roots and thus poor growth. Many have resolved this problem by first adding a 2″ to 3″ thick layer of gravel and then adding the clay pebbles. With this, media will stay in place.
Pro: Like clay pebbles and AquaRock, lava rock is lightweight. Because of its porous nature, it has tons of surface area for the nitrifying bacteria to attach to and grow. Lava rock is a somewhat less expensive option and easily purchased locally.
Con: The most obvious con is the rough nature of lava rock making it difficult to work with. Lava rock also has a tendency to break down leaving smaller particles in your system to contend with. Another common issue with lava rock is that it comes dyed. You will want to make sure to purchase a non-dyed version, which may take some homework time to find.
Though there are alternative grow medias such as Perlite, Vermiculite, Sand, Coir, or Glass beads, the above named four medias are the most popular. Which media is chosen is often a preference driven by the specifics of the individual system. Some growers even choose to use two medias together to provide a specific purpose or solution to a problem such as floating media. It is my hope after reading the information, you can make a more informed decision regarding which media you will choose and thus suffer less frustration caused by the trial and error method I have used.
I wish you nothing but the best of growing luck! If you like this article and would like more informative articles like it, please subscribe!