The urban gardener asked:


“Ebb and flow” hydroponics system is an example of the common arrangement of the indoor garden. Such system is composed of the upper grow bed, which is a box or tray that holds containers with plants. Those individual containers may be filled with various mediums, the most frequently used ones being rockwool, coconut fiber, lava rock, perlite, vermiculite or styrofoam pellets. The best mediums are those that are porous and can accumulate some water for a long time: lava rock is said to be the best in this respect.

The other part of the hydroponic system is the lower bed – the reservoir with the mix of water and nutrients dissolved in it.  Aquarium pump, regularly triggered by a timer, sends water solution up into the tray with plants.

The most important thing is to keep the correct composition of water solution in the reservoir – this is the key factor of the hydroponic garden flourishing. Many beginners find it difficult to maintain the right pH level of the water, necessary amount of nutrients, and their correct ratio. 

Standard organic plant nutrients are available to fertilize plants; however, many people are reluctant to do that, as they think such fertilizers will quickly make the water reservoir dirty. Indeed, organic nutrients interact with the organisms in water, which leads to their decomposition. Specialized concentrated nutrients, on the other hand, keep the reservoir relatively clean, since they are synthetically made and thus they cannot interact with the organisms in water. Nonetheless, such “clean” fertilizers will severely burn the plants roots if used in access.

Being pumped into the grow bed, water with a fertilizer saturates the plants and returns to the reservoir lacking the previous amount of nutrients and ppm (parts per million). Thus, its composition is always different and changeable. That is why a gardener should always monitor water solution, controlling its pH level and plant nutrients amount.

The urban gardener asked:


Soil less Mixtures

There is a great amount of soil less mixtures available, which contain different ingredients. Sphagnum moss, perlite, and vermiculite are the most widely spread hydroponics components, used in such mixtures.

Being organic, soil less growing media are usually used for container gardening wick systems or on-recovery drip systems. It is also possible to use soil less mixtures in recovery systems, however, it is necessary to remember that because of very fine particles in such mixtures, they can clog tubes, pumps and drip emitters, when used without a good filtration system. By the way, according to the urban gardeners, one can use panty hose as a filter: just fit it to the return line and to the pump inlet, and all the tiny particles will be filtered out.

Most soil less mixes form a good growing medium for multiple hydroponic and organic gardens, because they can hold water well, have great wicking action, and, at the same time, they provide a reasonable amount of air to the roots of growing plants.

 

Coconut Fiber

The popularity of coconut fiber as growing medium increases rapidly around the world. Being the first totally organic growing medium, providing highest performance for hydroponic systems, coconut fiber may soon become the most popular growing medium ever. It is interesting to note that coconut fiber is, actually, a waste product, which contains the powdered husks of coconuts.

In comparison to rockwool, coconut fiber is characterized with higher oxygen capacity and water retaining. These features are important advantages for hydroponic systems with intermittent watering cycles.

Coconut fiber also contains a lot of root stimulating hormones, thus offering some protection against fungus infestation and other root diseases. The mixture of 50% coconut fiber and 50% expanded clay pellets is considered to be the perfect growing medium.

However, it is necessary to underline one precaution when buying coconut fiber. Avoid purchasing a low grade coconut fiber, which is very fine grained and contains a high level of sea-salts. Such coconut fiber will have negative and disappointing effect on hydroponic system.

The urban gardener asked:


Hydroponics implies growing of the plants without soil; however, they still need medium to grow in. Hydroponics stores online or local ones offer a wide range of mediums to choose from, and it is better to know them to make the optimal choice.

Different Types of Growing Mediums

Although almost any substances can more or less serve as the growing medium, the most popular are those named below:

- Water / Air / Sand / Gravel

- Vermiculite / Perlite

 - Lava Rock

 - Sphagum Moss / Sawdust

 - Expanded clay pellets

 - Oasis Cubes

 - Coconut Fiber

 - Fiberglass Insulation

 - Proprietary Soilless Mix

 - Rockwool

Although rockwool is the last in the list, it can definitely be named the most popular growing medium among hydroponics gardeners, because it is easy and cozy to use.

Rockwool was initially used as insulation material in building. However, hydroponic gardeners in Denmark were the first to discover its advantages when used as a growing medium. Nowadays, rockwool is highly valued and commercially available in the forms of rockwool cubes and rockwool plugs. To produce rockwool stone and sand are melted together and then spun into various shapes and sizes, which sounds similar to the production of cotton candy.

Rockwool Advantages

Rockwool cubes (sized 36” by 12” by 3”) are very convenient to use, because they can be easily cut to a shape matching your needs. This material perfectly holds water and air, being very porous. Therefore, the roots of the plants will be protected both from rotting and drying out in case of the pump malfunction or other event long enough for you to be able to correct the situation.

 

The granules of the rockwool plugs keep together well and are not less easy to use.

Precautions

Unfortunately, rockwool has weakpoints as well, besides the benefits mentioned above. It can hardly be called environmentally friendly, as it is made of rock and thus does not bio-degrade, requiring some efforts to eliminate it. Moreover, it can be dangerous for the human health, causing silicosis if accidentally inhaled. For this reason, it is recommended to wear a face mask with a HEPA filter and handle rockwool carefully. 

One more thing, a gardener should keep in mind while using rockwool, is that this material has a very high pH level, which should be reduced with available acidic substances and regularly checked.

In spite of the rockwool cons, it is still so easy and comfortable to use that it remains the most popular growing medium type among the hydroponics gardeners. The only thing to do is to take necessary precautions while working with it.