Aquaponics Grow Media

credit to : Farm Tech Mart
link : http://farmtech-mart.com/grow_media

Although there is no soil in a hydroponic garden, the plants must still be anchored. There is a wide range of inert materials which can be used to support plant roots and we call them "growing mediums". Clay Pellets, Perlite, Vermiculite, Coconut Fiber and Rockwool are the most popular media. The hydroponic media that work best are pH neutral, provide ample support for plants, retain moisture, and allow space for good air exchange. The type of media you choose will depend on the size and type of plants you wish to grow, and the type of hydroponic system being used. 

1. Clay Pebbles (LECA) 

Expended Clay Aggregate pebbles (LECA) main use is as a hydroponic growing media in flood and drain and dripper hydroponics systems like the Wilma. Clay pebbles can also be mixed with other hydroponic growing media like Cellmax, Coco or Soil to give better aeration. To create better drainage when growing in pots add a layer of Clay pebbles in the bottom.

Many growers use clay pebbles as a hydroponic growing media because they have excellent aeration and drainage properties. Clay pebbles are a clean, ph stable, and can be reused a couple of times before they need to be replaced.

Flood and drain or a dripper system will deliver the fast growth rates and yields using clay pebbles.

The centre of a clay pebble is honeycomb to make it light weight and the outside of a clay pebble is covered in a thin layer of solid clay making them suitable for use in hydroponics.

Tired of looking at dirty soil on the top of house plants in pots why not use some clay pebbles to make it look more attractive.

2. Perlite

Good old perlite! It's been around for years, mainly for use as a soil additive to increase aeration and draining of the soil. Perlite is a mined material, a form of volcanic glass that when rapidly heated to more than 1600 deg. f. it pops much like popcorn as the water vaporizes and makes countless tiny bubbles.

Perlite is one of the best hydroponic growing mediums around. Used by itself or as a mixture with other mediums. Perlite is commonly used with vermiculite ( a 50 - 50 mix is a very popular medium), and is also one of the major ingredients of soiless mix's. Perlite has good wicking action which makes it a good choice for wick-type hydroponic systems. Perlite is also relatively inexpensive.

The biggest drawback to perlite is that it doesn't retain water well which means that it will dry out quickly between waterings. The dust from perlite is bad for your health so you should wear a dust mask when handling it.

3. Vermiculite 

Vermiculite is another mined material. In it's natural state it resembles mica rock, but when quickly heated it expands due to the generation of interlaminar steam.

Vermiculite is most frequently used in conjunction with perlite as the two complement each other well. Vermiculite retains moisture (about 200% - 300% by weight), and perlite doesn't so you can balance your growing medium so that it retains water and nutrients well but still supplies the roots with plenty of oxygen. A 50/50 mix of vermiculite and perlite is a very popular medium for drip type hydroponic systems as well as ebb and flow systems. Vermiculite is inexpensive.

The major drawback of vermiculite is that it retains too much water to be used by itself. It can suffocate the roots of plants if used straight.

4. Coconut Fiber 

Coconut fiber is rapidly becoming one of the most popular growing mediums in the world. In fact it may soon be THE most popular. It is the first totally "organic" growing medium that offers top performance in hydroponic systems. Coconut fiber is essentially a waste product of the coconut industry, it is the powdered husks of the coconut itself.

There are many advantages - it maintains a larger oxygen capacity than rockwool, yet also has superior water holding ability than rockwool which is a real advantage for hydroponic systems that have intermittent watering cycles.

Coconut fiber is also high in root stimulating hormones and offers some protection against root diseases including fungus infestation. Dutch growers have found that a mixture of 50% coconut fiber and 50% expanded clay pellets is the perfect growing medium.

One word of caution about coconut fiber, you must be careful when you purchase coconut fiber. There is a commonly available, lower grade of coconut fiber that is high in sea-salt and is very fine grained. Lower grade coconut fiber will lead to disappointing results when used in a hydroponic system.

5. Rockwool

Rockwool is a very popular hydroponics growing medium. Rockwool is a porous substance that forms when a mixture of rocks, mostly basalt and dolomite, is melted at high temperature and specially processed. Given the material's neutral nature, it is used to build plant-growing medium granules or slabs, blocks, plugs, cubes, etc.

Rockwool provides roots with a good balance of water/oxygen As rockwool is composed of 97% air, it is easy to control the air/water ratio in it. Its porous quality also enhances root growth.

. Small cubes are used for starting seeds and cuttings, 3" or 4" cubes for small plants or intermediate growth, and slabs for larger plants. Rockwool can be used with continuous drip or flood and drain systems. Although it is possible to sterilize and re-use Rockwool, most often it is used only once.

More than 95% of all greenhouse vegetable production is carried out with the help of Rockwool -and for good reason. Like mentioned before, rockwool allows control over air and water supply, which are essential factors for plant growth. It also provides other feasible conditions to support a great crop, leading to consistency in plant production and yield, which is an important consideration in commercial harvesting.

Another pro is the easy availability of Rockwool products in a variety of shapes and sizes. This promotes the maximum utilization of Rockwool in various types of hydroponic set-ups.

Different Types of Aquaponics Systems

There are three different types of aquaponics systems that have been developed for use by home gardeners and commercial enterprises. These are media based, NFT and Deep Flow or Raft systems and here is a description of each one.

Media-based: also known as the gravel bed system, the media-based aquaponics system is the simplest type to set up and can be used on a small or large scale. This is why it is the type most commonly used by backyard aquaponics enthusiasts. Containers are filled with small rocks, usually expanded clay pebbles which are porous to absorb water and air, and then seedlings are planted directly into these. Water from the fish tank is circulated through the container to allow the plants to access the nutrients. The rocks act as a biological filter as well as a solids filter, eliminating the need for extra equipment.

You can also use special netted growing pots for your seeds or seedlings. You fill these with perlite, coir, peat moss or the clay pebbles and plant into them. These pots are then placed into a larger container which has been filled with the expanding clay pebbles, making sure the netted sides are covered by the media. Media-based aquaponics systems hold plants firmly and so are ideal for growing fruiting plants.

There are two different ways this type of aquaponics system can be operated. The first method pumps a continuous flow of water through the media bed from the fish tank and back into the tank. The second is a process called flood and drain or ebb and flow, where water is pumped into the bed to a depth of about 10 to 12 inches (20 to 30 cms) and then drained away. A timer controls the flooding and draining sequence.

NFT system: or Nutrient Film Technique is a common method used in hydroponics that is best suited to a large-scale aquaponics production. This is because of the expense of setting up the system of PVC pipes and mechanical filtration needed to operate the system. Because there is not the surface area exposed to the air, as in the media-based system, a biological filter is needed to allow the beneficial bacteria to develop and convert the fish wastes into plant nutrients. Solids filtration is also needed to deal with the solids in the fish waste; this is usually set up in a separate tank through which the water passes before going through the plant pipes.

In the NFT system, plants are held in netted growing pots which are suspended through holes cut in the pipe. A thin film of nutrient-rich water is run along the bottom of enclosed gutters so that the roots can reach it. It is really only suited to plants that have a small root systems, such as leafy green vegetables.

Deep Flow: also called Deep Water Culture (DWC) or the Raft system, this is another commonly-used method in hydroponics. This system involves the use of a foam ‘raft’ that floats on top of the water. It is a popular choice for both commercial and backyard aquaponics because it is relatively cheap to set up and operate.

A container or channel is used to hold the water as it is pumped through from the fish tank, after it has been filtered to remove any solid waste. Plants are held in holes made in the raft, so their roots dangle down into the water. This method uses high volumes of water which provides stable water temperatures for the plants and fish. It is the method most often used in commercial aquaponics operations because of the ease with which the plants can be tended and harvested. Again, it is better suited to growing herbs and leafy green vegetables than plants with bigger root systems and fruiting varieties.

This type of system can easily be adapted for home garden use by simply floating a styrofoam tray on top of a fish tank. Just cut holes in the tray and suspend the plants, or plants in netting pots, through the holes so the roots are in contact with the water. Choose fish varieties that are not voracious plant eaters to avoid having plants’ roots eaten away.

Now that you understand how each of the 3 types of aquaponics systems operates, you will be in a better position to decide which one suits you the best. Whichever method you choose, it is best to start small so you can gradually build your expertise and experience before setting up a large system.

   

Aquaponics Variety

Types of common fish and vegetables suitable for Aquaponics

Vegetables

Most of the common garden vegetables do well with aquaponics, except for a lot of the root vegetables like potatoes, onions, garlic, etc. Growing root crops with aquaponics is possible but they can be tricky in this kind of deep water raft system, perhaps media fill system could do it.

Common fruit bearing vegetables like tomatoes, cucumbers, okra, squash, peppers, melons, strawberries and even corn if supported will grow beautifully. Leafy greens like lettuce, cabbage and herbs like basil grow amazingly well.

Common legumes like beans and peas also do quite well. Viney plants like pole beans and cucumbers are great because they can be rooted in the grow bed, and the rest of the plant can grow off in some direction and take advantage of space and light away from the grow bed.

Fish

Tilapia, a fresh water fish that is hardy and fast growing, is most commonly raised fish in aquaponics. Numerous other freshwater fish, such as crappie, bass, carp, brim, goldfish and koi are being raised in aquaponics. More intense commercial operators are experimenting and developing hybrid systems to raise trout, char and salmon, such systems are more complex and require higher levels of technologies and management for rearing environment control.

Here are a short list of suitable fish for Aquaponics:
Tilapia
Walleye
Yellow Perch
Lake Perch
Bluegill
Channel Catfish
Hybrid Striped Bass
Northern Crayfish
Largemouth Bass
Smallmouth Bass
All Carp
Goldfish
Sunfish
Bream
Crappie
Pacu
Koi

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