How Floating Raft Aquaponics Works: Animation

Murray Hallam next to a commercial DWC Floating Raft System

For a long time Floating Raft Aquaponics was shrouded in mystery as many people tried to penetrate its “inner secrets” of what it all meant. Terms like Swirl Filters and Particulate Filters were bandied around and it all looked terribly difficult to understand to the casual observer.

Floating Raft or DWC (Deep water culture) is more suited to commercial aquaponics operators to make it easy to mass produce certain types of vegetables, namely lettuce. In order to do that, the lettuce seedling is placed on a floating raft, usually made of a large polystyrene sheets where a number of holes are cut out to accommodate the roots of the plants.

Solids removal is the key to successful floating raft. The reason why various filters are necessary is quite simple.

The plants roots are heavily oxygenated.
The roots themselves are immersed in water all the time. Dirt particles need to be eliminated as the dirt will adhere to the white roots of the plant and actually block the plants roots from taking up the vital oxygen and minerals that will enable the plant to mature and grow.

Hence the need for an adequate system of filtration.

Domestic Floating Raft System

Having clean oxygenated water is essential to success.

When Murray Hallam built his first domestic floating raft kit he built in the same filtration systems as he uses on his commercial systems.

When the fish solids leave the main fish tank which can be based on the CHOP system, water is pumped through a swirl filter at a slower pace than seen on this animation. Water traveling through a swirl filter can appear to move very slowly. The idea is to use as wide a swirl filter tank as possible so solids will travel slowly and settle in a spiral nebula pattern on the bottom of the tank.
These solids are later pumped out to a compost worm farm and processed into a conventional garden bed as a source of high fertilizer.

Commercial Swirl Filter with Murray Hallam

From the swirl filter the water enters the Particulate filter.
Here large filters screen waste through a series of 3 to 6 dense screens that are heavily oxygenated before entering a series of drop out zone troughs.
Mineralization of plant nutrients usually occurs in the particulate tank.
You’ll notice from the animation extra aeration is added between the filters. Bacteria is active in this area converting the suspended fish solids that are caught here into nutrients that the plants require.

Particulate Filter

These nutrients are now in a soluble form and are easily carried by the water to the plant roots. Towards the end of the Particulate Filter are a series of Drop Out Zones.

These are hard barriers that allow the water to skim over the surface very slowly. The barriers pacify the water and allowing any suspended solids to be further removed from the system. The water is then pumped on its way to the floating rafts.

Swirl Filter detail with settled fish matter

The floating raft system uses a number of air stones at regular intervals to heavily oxygenate the plant roots. Water that enters this area should by now be free of most solids. Plant roots should be clean and white looking. Lettuce here will grow rapidly.

Harvesting the lettuce can now be carried out easily.

More information on making money from Commercial Aquaponics can be found in the Aquaponics for Profit video clip or you can purchase the Aquaponics Secrets Video packed with over 90 minutes of quality easy to understand information, graphics and animation as taught by Aquaponics guru Murray Hallam.