In commercial aquaponics, the most common grow bed is the raft system. There are two more grow bed designs, the NFT or Nutrient Film Technique and the media-filled grow bed. Even though media-filled beds are not so common in large production scales, it is the favorite of most aquaponics hobbyists. NFT on the other hand is the least preferred of the three designs because it requires more maintenance.
The raft system is highly advisable in commercial aquaponics because of the large production it yields. Media-filled beds don’t get to produce as much. Raft system allows for higher stocking densities and in businesses, the more sales the better. Initially, the raft system requires more water to complete but the water flow benefits the health of the fish.
The raft system allows for a higher stocking density of fish because of the water that is constantly flowing through the channels. This requires five to eight times more water than the normal. Because of the high volume of water, this makes the number of fish per gallon of water lower and therefore makes managing of the water easier.
In this design, the plants are placed on rafts made of Styrofoam. Only the roots of the plants are in constant contact with water. These rafts are arranged in a way that forms channels underneath to allow the water to pass through each root but before the water goes to the plants, it is first filtered to remove large particles so as not to cause clogging in the drainage. After flowing through plants’ roots, the water drains back into the fish tank and cycle goes on.
Solids capture – is a very important process in raft systems. If these solids are not removed from the system, over time they will build up in pipes and drainage and might even change the water level into something toxic for your plants and fish. It can also cause solids to coat the roots of the plants and will affect their ability to absorb nutrients.
Filtration system – is another important component in a raft aquaponics. The filter will help maintain a clean water for your system so that you won’t have to do a complete cleaning which is actually discouraged because it prevents bacteria to grow and multiply.
Sump tank – this is optional in a raft system but is used by many. A sump tank is located lower than all the other tanks in aquaponics. The water from the grow beds drain into the sump tank and when it reaches a certain level, the water is pumped back into the fish tank. The sump allows oxygenation of water numerous times each day.
Degassing and pH adjustment tanks – These two tanks are optional but help in the maintenance of the water levels. The degassing tank is where the water is made to release gas before going back into the system. The pH level adjustment tank is usually but not necessarily a separate tank where the water is slowly added base or acid to get the right pH level.