Hydroponic cultivation need not be complex or expensive, and requires only a little more equipment than indoor growing using soil.
Hydroponic growing differs very little from soil growing. The plants grow and flower in the same light cycle and are fed the same nutrients – nitrogen, phosphorus and potassium (N-P-K,
plus micro-nutrients and trace elements). The main difference is that hydro plants root and grow in a neutral medium which, unlike soil, has no nutrients of its own.
Hydroponic nutrient is water soluble and is immediately available to the plants when applied to the growing medium, while organic nutrients must be broken down by bacteria in order to enrich the soil to which they are added.
Aside from the indoor basics of light(s), timer, fans and air exchange (all of which are required for indoor soil growing, of course), hydroponic growers will require two meters for testing the nutrient water they give to their plants.
- An electrical conductivity or EC meter measures the amount of nutrient in the feed water and presents it as a simple number, allowing growers to be sure that they do not over-feed or under-feed their plants. Nutrient meters in different regions and countries may measure in other scales: TDS (total dissolved solids) or PPM (parts per million).
- A pH meter tests the acidity/alkalinity of water. Cannabis prefers an acidic growing medium, so hydroponic feed water is usually lowered to around pH 5.8.
- Most growers will also require a substance for lowering and/or raising pH. Tap water typically has a higher pH than ideal for hydroponic cannabis, so it usually must be lowered. Household products such as lemon juice or vinegar are sufficiently acidic to lower pH.
In addition, hydro cultivation will require a hydroponic growing medium, such as rock-wool (ideal for starting seeds and clones) or expanded clay-balls (a re-useable medium and an excellent second stage for plants that start in rock-wool), and hydroponic nutrient for the growing and the flowering stages.
In this diagram, plants are growing in rockwool slabs. The reservoir is filled with nutrient water, and contains a pump(attached to a timer) which delivers feed-water to the slabs several times per day.The slabs are inclined so that excess water runs off and flows back to the reservoir.