I have seen several different terminologies lately related to Aquaponics such as “Raft” or “NFT” and of course what I have been using since I started mine the “Media Bed” version. So I decided to familiarize myself more with the different types of systems and related “Pros” or “Cons” and share with you my findings. As most of you probably already know, we are currently using two of these systems at the moment (NFT & Media bed) and I am planning on adding a raft system possibly as early as this weekend. Below is a break down of each of those systems.
Media Bed – (using a substance such as lave rocks or other medium other than soil for raising plants and bacteria)
A media-filled bed system uses a container filled with perlite, lava rock, gravel or another media for the plant bed. This method appears to be the most common among back yard users and requires no additional filtration, making it very simple to operate. The container is flooded with water periodically from the fish tank. Once full, the water then drains back to the fish tank, usually using a bell siphon or flush kit (such as those used on a toilet system). Solids from the fish waste are broken down within the plant bed using beneficial bacteria’s and in some cases worms to increase the break-down of the waste. I have read recently though, that the production from this set-up is much lower than the next two systems I will cover next.
Raft – (using foam boards with cut outs to place planter pots floating in fish water)
A raft system uses Styrofoam boards that float on top of the water where the plants are grown. Water is pumped from the fish tank into the raft tank where the plants are grown and then back to the fish tank. This is usually a tank separate from the fish tank. The beneficial bacteria needed to convert the ammonia’s created by fish waste are able to live in the rafts much like that of the media bed system. Using a separate tank to grow the plants (rather than the fish tank) provides a buffer for the fish, reducing stress and potential water quality problems. Most large scale operations I have studied online use this type of system or the “NFT” system for commercial grows like those found in large green houses.
NFT – (using PVC pipes or similar materials with cut outs for plants using a continuous flow of water)
The Nutrient Film Technique (NFT) is a system whereby plants are grown in long narrow channels such as PVC pipes or box channels with cuts lids for plants. A continuous flow of water travels down each pipe providing plant roots with an ever flowing fresh supply nutrient and oxygen rich water. Due to a lack of surface area commonly found in media beds or rafts, a bio filter is usually required to allow for the beneficial bacteria to live and cultivate. I have read that using small hoses like those commonly used in Hydro-ponics are not as effective and prone to clog when used in Aquaponics due to the organic nature of the system and “living” water. I have found this type of system very popular especially in South American systems and of course the standard in Hydro-ponics.