In March, we discussed lighting systems, which are a crucial factor in any hydroponic setup. We will now examine tools of the trade and their influence on environmental control.

Beyond the tools we have discussed, as well as those you are already familiar with (pumps, generators, fans, reflectors, timers, cameras, fertilizer injectors, dehumidification and air conditioning systems), there are numerous instruments and devices tailored to the field of indoor gardening. The inclusion of this equipment in your setup is highly recommended (if not required) to enable a healthy, abundant, high-quality harvest. All of these tools allow you to closely monitor, manipulate, create and control the environment(s) of your crops.

Water analysis

Before we start growing, it is vital that we understand what is in our water in its natural state (as it flows from the well or faucet, before we have added additional nutrients). This varies by topography, region, city and by source. The most effective analysis is performed in a lab. The lab will list all elements (ex iron, chlorine, calcium, manganese, sodium and other trace minerals and contaminants) and their amounts contained in your water. The results will not only provide information about what is there, but will shed light on what type of filtration systems need to be utilized to remove unwanted materials.

Water filtration

Major classifications of water filtration systems include carbon (sediment) filtration systems, ultraviolet sterilization systems and reverse osmosis systems. Carbon filters, or pre-filters, excel at removing large particles like silt, iron and other trace minerals. As water passes through the filter, activated carbon attracts and absorbs unwanted material in your water. A drawback is that it is largely ineffective at removing salt from the water. If your water has a high degree of salinity, you will need additional filtration. Ultraviolet systems use UV radiation to eradicate bacteria found in the water. Although it removes bacteria effectively, it lacks range to remove much of anything else. Reverse osmosis systems are a trusted choice of indoor gardeners. In an R/O system, water is pressurized and pushed through a semi-permeable membrane. The contaminants cannot fit through the membrane. Some systems can remove particles as small as 1/1000 of a micron in size. The clean water that made it through the membrane is ready to use whereas the stuff that cannot fit is expelled through a separate hose. Efficiency of R/O systems is measured by the amount of clean water produced versus the amount of wastewater generated.

PH meters

A pH meter measures hydrogen – ion concentration in a solution, indicating its acidity or alkalinity. The scale ranges from zero to 14, with zero being extremely acidic, 7 being neutral and 14 being extremely alkaline. It is a logarithmic scale, meaning a substance with a pH of 5 is 10 times as acidic as one with a pH of 6. Likewise, a substance with a pH of is 10 times as alkaline as one with a pH of 8. Most plants prefer a mildly acidic solution, but needs vary by crop as well as stage of development.

Electrical conductivity (EC) meters

EC meters measure the ability of the solution to conduct electricity. Pure water does not conduct electricity, so readings above zero indicate the presence of something that does. Conductivity meters are also known as PPM (parts per million) meters or TDS (total dissolved solids) meters. By multiplying electrical conductivity by a conversion factor of 500 (US) or 700 (European), we can arrive at the PPM of the solution. Consider the source of your fertilizer when choosing which conversion factor to use. Although this is a starting point, absolute numbers will only be reliable if starting with a solution that has zero ppm. If that’s not possible, consider using relative readings. For example, if we need the nutrient blend to have a conductivity of one (PPM = 500), and the original source had a conductivity of one-half, we need a final EC of one and a half.

There is a substantial amount of variance in the PPM that various crops prefer. Lettuces, okra, mint, parsley, sage, thyme and other herbs require a relatively low amount of fertilizer, and are happy with a PPM as low as 200 to 400. Beets, blueberries, cabbages, peppers, strawberries and tomatoes need more fertilizer and may prefer a PPM closer to 1,000 to 1,500.

Because most fertilizers are slightly acidic, we can use EC and the pH levels to monitor nutrient uptake by the plants. If EC goes up and pH goes down, that indicates too strong of a nutrient solution. If EC goes down and pH goes up, nutrient levels should be increased. If EC and pH levels are constant, nutrient levels in the solution are just right.

Read more: Hydroponics 101: What Is Hydroponics?

Reservoir chillers

A reservoir chiller, or nutrient chiller, keeps the temperature of the nutrient solution in a predefined range. If a nutrient solution becomes too hot, the amount of dissolved oxygen decreases, which could lead to poor root growth, poor overall growth and a much higher chance of root diseases like pythium. Deep water culture, nutrient film technique and ebb and flow systems benefit most from use of a chiller.


Make sure to include use of several to determine hot spots, variances and ranges of temperature and humidity within your environment throughout the day and crop cycle.

Light meter

A light meter, or photometer, measures the amount of usable light a plant is receiving in foot-candles. It is useful in determining where to place crops based on their lighting needs, as well as which crops or areas may require supplemental lighting.

Carbon dioxide supplementation

Depending on your crop and level of ventilation, your environment may benefit from additional levels of carbon dioxide (CO2). CO2, a key component of photosynthesis, is found in trace amounts in the atmosphere. It comprises about 4/100 of 1 percent (400 parts per million or PPM) of the air we breathe. However, if growing in a sealed environment, composition of the air will contain less CO2 as the plants utilize it and release oxygen (O2) into the environment. When coupled with the fact that most produce would prefer a mixture of about 1,000 PPM, the need for CO2 supplementation becomes evident. Most CO2 generators create additional CO2 by burning a hydrocarbon fuel, usually propane or natural gas, of which CO2 is a resulting byproduct. Systems should include a regulator or timer, as increasing CO2 levels beyond approximately 2,000 PPM can be toxic to plants.

Read more: Hydroponics 101: Lighting Systems