Aquaponic planting media is media in which plants are grown in aquaponics system. This media act like soil for the plants in traditional farming. There are some aquaponic planting media that commonly use, those are raft, MFT and media filled beds.
Raft method (float, deep channel)
This system use polystyrene board as raft that floating on the water to grow the plants. Usually this raft is located in tank that separate from fish tank. Water from fish tank flow thru water filtration unit before come to raft tank where the plants are grown, and flow back to fish tank. The useful microorganism are living in raft tank and entire system. It became one of raft system advantages
NFT (Nutrient Film Technique)
NFT is methodology to grown plants in small and long channels. Water rich in nutrients and oxygen supplied to the plants thru a thin layer of water. Just like raft method, water runs continuously from fish tank to purification elements and then to the plants that grown on NFT channels, and flow back to fish tank.
This method use a container with growing media inside it like lava rock or gravel called as growbed. Fish tank water flooded the growbed in specific time interval to give nutrient to the plants. After that water flow back to fish tank. The waste from fish tank is broken down in this growbed. This system need no purification element, and simple since use less elements.
So, what is the function of growbed. Its function is to:
- Provide plants with place to grow and spin their roots
- Keep the temperature around the roots of plants
- Provide media for nitrifying microorganisms to build their colony
- Serves as water filtration element
- As a home for useful earthworm
There are also some consideration to choose prefect growbed for your aquaponic system:
- Media should not break down easily, since it will make the water turbid and change pH and nutrients.
- Must have neutral pH
- Free from contaminants in order to keep water quality
- Can drain the water well to ensure the root don't get waterlogged.
- Have good shape so that oxygen can circulate properly
- Size of grow media must be perfect. If it is too small it will clogged up easily by waste and will cause of bad circulation of water and air for the root. If it is too big it will prevent the plant to grow upright.
Then, what material you can use for your growbed?
Expanded Clay Pebbles - a type of Lightweight Expanded Clay Aggregate (LECA)
LECA is clay-based pellet that grows whenever soaked and it is soil-like layer that root base can simply expand in to. Furthermore, the pebbles tend to be comparatively sleek, easy to handle by hand and suitable for sensitive root base. It relatively have wide surface that is good for microorganism to live and grow. Have neutral pH, won't have an impact on the water, hence detrimentally impacting on plant progress. It can drain easily that is good for roots to have oxygen.
Lava rock is very common to use since it availability and low cost. It is lightweight and porous material with irregular shape
River gravel or river stone
In general river gravel is cheap and readily media. Its high density make it easy to support tall plants. On the other side of the gravel cannot hold water well, heavy and has a small surface area, so it cannot properly support the microorganisms.
Which media is the best?
This would depend on your situations, location and what kind of plant will be planted. LECA is the most popular, it is slightly expensive. Whenever possible it is good to use lava rock since it have same benefit with less cost. River gravel is also common because of its availability around the world and its low cost