Richard bray

Fish & Fish Tanks
Remember; fish waste feeds the bacteria in your system, which in turn feeds the plants. Media-filled beds provide a large amount of biological surface area (BSA) for bacteria to colonize, which gives them the ability to transform large amounts of waste.
DWC systems don’t have the same amount of grow media, which can make it more difficult for bacteria to do their jobs. This can result in a system that is unable to support a high stocking density because the bacteria can’t keep up with the waste. When you choose fish for a DWC system, select fish that thrive in a low to medium stocking density, and like slightly cooler water temperatures.
148
The material for a fish tank should meet the same standards as the materials for the rest of your system. Deep tanks are preferable to shallow tanks because they maintain water temperature easier, and give fish a more comfortable habitat.
Plumbing & Filtration
Most DWC systems are continuous-flow with a solids filter and BSA filter. The solids filter allows solid waste to settle out of the system, which gives bacteria the chance to mineralize the waste and release nutrients. The BSA filter provides a large surface area for nitrifying bacteria to transform ammonia into nitrogen.
The solids filter is usually placed after the fish tank and before the grow beds, while the BSA filter can be anywhere in the system, but usually comes after the grow bed and before the fish tank. Healthy filters are vital to the health of your aquaponic system, so make sure your filters are large enough to handle the amount of waste your fish will produce. This will also help your system support a higher stocking density, which will result in a higher nutrient content.
A deep-water culture system will be more complex to build, but it is much easier to scale up for a variety of growing goals. Luckily, many of the materials are easy to find for free.
149
Building a DWC System
Deep-water culture aquaponic systems work best for growers who want to specialize in certain crops, and who want to have a larger fish harvest. These systems are more versatile with their setup, but they do require external filtration to make up for the BSA lost by not having a grow media.
Make sure all materials used in your system meet the requirements laid out in the deep-water culture chapter.
A basic DWC aquaponic system is made up of the following components:

• Fish Tank
• Aerator
• Water Pump
• Grow Bed
• Siphons
• BSA filter
• Solids filter
• Timer
• Sump Tank
• Plumbing

150

There is one simple DWC system that can be scaled up to meet the demands of a small profitable operation. IBC totes are the easiest building material for these systems, although the design can be modified to use stock tanks or plastic-lined frames with the same volume.