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:


 

Along with water, hydroponics plant nutrients, CO2 and oxygen, grow lights is the key basic component, required by plants to live. Providing additional light is necessary for indoor gardening. Furthermore, light should resemble the sunlight as much as possible. The major concern with other types of lights is that they do not produce light in the appropriate spectrum, required by plants.

Being the most efficient bulbs, HPS bulbs are commonly used by gardeners. Producing light in red and yellow spectrum, light generated by high pressure sodium lamps resembles the natural sunlight during autumn. Due to this peculiarity, HPS light is the best for promoting plants blooming. However, some plants may react negatively to this type of light, growing with oblong stem, etc. To address that issue, new HPS bulbs with color correction have been developed. For example, Son Argo feature properly balanced light spectrum, which suits perfectly for the needs of indoor gardening.

High pressure sodium grow lamps are made of a semi-transparent ceramic arc tube, filled with a mixture of sodium, mercury, and xenon. The arc tube is placed into the protective outer glass shield, similarly to metal halide bulbs. The power ranges of HPS bulbs vary from 35w to 1000w, while the most popular are 250w, 400w, 600w and 1000w.

HPS bulbs are more durable in comparison with MH bulbs: they can be replaced once every 24 months. Though HPS grow lights lose their brightness slowly, in order to keep the brightness at the steady level, it is still recommended to replace the bulb within the specified period.

Among the brand new types of grow lights are sulfur lights, which are said to feature extremely high brightness and effectiveness. However, these bulbs are still rare on the market in view of the high price, so it is early to evaluate their practical value for those gardeners, for whom indoor hydroponics growing remains a hobby.

The urban gardener asked:


Along with water,  hydroponics plant nutrients, Co2 and oxygen, grow lights is the key basic component, required by plants to live. Providing additional light is necessary for indoor gardening. Furthermore, light should resemble the sunlight as much as possible. In order to achieve that goal several types of lights are used: incandescent, fluorescent, high intensity discharge or HID lamps and sulfur lights. While there are many other types of lighting, only the mentioned above are recommended for indoor gardening. The major concern with other types of lights is that they do not produce light in the appropriate spectrum, required by plants.

Though typical widely used incandescent lamps fit any ordinary light socket, this type of lighting is considered to be the least effective in lighting your garden in comparison with other types of lighting. Incandescent lights produce light in the red spectrum; that is why such lamps are commonly covered with a blue coating in order to increase the amount of blue spectrum in the produced light. In general, incandescent lights are considered to be poor options for indoor gardening needs.

In comparison with incandescent lamps, fluorescent lights produce more light with lower energy consumption. However, the light, produced by fluorescent lamps, is not intensive enough and cannot penetrate more than 6” – 8”. Light, produced by fluorescent lamps, is usually simply insufficient to provide normal growing of plants, vegetables and flowers. The only application, where it is possible to use fluorescent light, is growing seedlings, cuttings, or some particular plants with low light requirements, such as orchids.

High intensity discharge lights, also known as HID lights, are currently the most effective lights for indoor gardening. Metal halide (MH) and high pressure sodium (HPS) grow lamps are two major types of HID lights. Each type produces light in a particular range: for example, metal halide lights generate blue spectrum light similar to the full summer sun, and high pressure sodium lights produce light in red and yellow spectrum, resembling the autumn sunlight. 

Though high pressure sodium lamps usually are more expensive (by about 10%-20%) than metal halide lamps, they are more durable with extended lifecycle. Besides, HPS lights feature higher lumen output (97-150 lumens per watt consumed) and lose only about 5% of their brightness after one year of use (for comparison, MH bulbs produce about 70-115 lumens per watt and  lose up to 15-20% of their initial brightness within a year). 

Irrespectively to the particular type of lighting in use, it is recommended to replace lights on the timely manner: MH bulbs – after 12-18 months, and HPS bulbs – after 24 months of work. Basically, metal halide lamps is the more preferred type of lighting for plants, when they grow, and high pressure sodium lamps suit best for flowering plants. However, the discussion on which type of lighting is best is still open among gardeners. Each type of lights offers its own advantages, as well as disadvantages, so it is often a matter of personal choice, preferences, growing environment and needs. The scope of this article is to provide plain information on the available types of lighting for indoor hydroponic gardening, while leaving readers enough space for personal decisions on which product to prefer.  By the way, recently a new type of lights appeared. The so-called conversion systems allow switching between MH and HPS lights when it is necessary simply by changing the bulb. Though this type of lighting offers certain benefits, conversion systems are still pretty expensive. More information on particular types of HID grow lights used in hydroponics systems will be provided in the next set of hydroponics guides.