Richard bray

Pros: Cons:
• Simplest system to build • Extremely heavy; immobile
• Little to no extra filtration needed • Most expensive to build
• Supports the widest variety of crops • Labor-intensive
• Provides the best root support • Must clean media off roots for harvest
• Holds the most nutrients • Fluctuating water level stresses fish
93
Pros: Cons:
• Can add worms for more nutrition • Slower growth rate than raft systems
• Can be sized very small for class settings • Not suited for large operations
Growing Media
The media, or substrate, that forms the foundation of this system serves four important functions:

• It holds bacteria that turns fish waste into plant nutrients
• It helps oxygenate the water for plant roots and fish
• It serves as a habitat for redworms, which clean the water and provide extra nutrition
• It helps support tall plants

There are a few different options for the substrate you will use in your beds, but they all need to meet four basic requirements:

• Neutral pH
• Inert; meaning it can't break down
• Small enough to allow roots a firm foundation, but large enough to not clog pipes
• Porous enough to allow bacteria to grow on the surface

There are four different growing mediums that meet these requirment
94

Pros/Cons Clay
Pebbles River Rock Lava
Rock Vermiculite
Lightweight X X X
Smooth X X X
Porous X X X
1” Median Size X X
Estimated Weight per cu’ 261bs lOOlbs 441bs 61bs
Estimated Cost per cu’ $15-$20 $10-$12 $10-$12 $5-$8
Estimated Cost to fill a 4'x8’xl4” bed $550- $800 $370- $450 $370- 450 $200-$310
Of these, clay pebbles and river rock are the most common. Lava rock has sharp edges, which can damage roots easily, and vermiculite is small and can clog pipes and filters.