The Decider


The Coreconduit: Garden Controller System was the first version of the hydroMazing project .  The author of the Instructable drones on and on about healthy plants requiring attention and boredom until,

“…I’ve programmed into the Arduino a function I called, “TheDecider” that makes decisions based on maintaining optimum environmental conditions for growing plants. I added 2.4Ghz Wireless Radio Transceiver modules and a modular receiver system so that data is transmitted to within 1000 feet.”

TheDecider” was originally hardcoded with specific values that were fixed in place until I changed them in the Arduino sketch, recompiled, and uploaded.  There are two types of decisions that TheDecider executes, timed-based, and sensor-based rules.  The time-based rules simply compare the current time to the last time the appliance was turned-on or off.  The sensor-based rules use a minimum value threshold and a maximum value threshold that are compared to the current sensor reading and then execute the corresponding action for the appliance.  For example, if the temperature is below 55° then turn-off the ventilation fans; if the temperature is above 80° then turn-on the ventilation fans.  Each appliance has corresponding rules for sensor reading thresholds, time-based automation, and a combination of both, priority depending on the order of the rules.

Today’s hydroMazing uses the Raspberry Pi to provide an interface to the rules and the notifications.  The Pi communicates with the Arduino Nano microcontroller wirelessly sending updates and receiving data. TheDecider is a rules engine that executes the checks sent to it from the Pi.  The settings are stored in the EEPROM of the Arduino Nano allowing it to operate without further communications with the Pi.  hydroMazing doesn’t require an Internet connection to operate with the exception of receiving emails or text-alerts.  The Raspberry Pi can be configured to operate only within your WiFi network and be allowed to send emails and text-alerts.  Or, you can configure your router to allow access from outside and even assign a domain name, such as  See my Instructables for steps to a secure Pi.


hydroMazing Nutrient Controller

hydroMazing outside the box
hydroMazing outside the box

The hydroMazing smart garden system is designed to monitor and manage your growing environment by automatically controlling fans, heaters, lights, water pumps, and now, the nutrient solution.

The nutrient solution level of the hydroponics container system must be monitored.

As the nutrient solution level decreases it needs to be replenished with fresh water, otherwise the nutrient solution becomes more concentrated and some plants won’t respond well.  The hydroMazing Nutrient Controller can activate a pump that adds fresh water to bring the concentration back to the level it was when started, often referred to as “topping-off.”  The hydroMazing Nutrient Controller will also monitor your pH and EC, activating pumps to manage the solution, and notifying you when you need to make changes.

There is no need to adjust your pH or EC until it is necessary.

This is a big one!  There is a lot of misinformation out there about keeping the pH and EC regulated.  If I were paranoid, I’d say it was a conspiracy from hydroponics manufacturers and retailers who want to sell more consumable product.  Don’t get me wrong, proper pH and EC is important, even critical, to the success of a plant.

The pH of water is an important measurement whether you are gardening indoors or outdoors, soil or soil-less, because it affects whether a plant can properly take in nutrients.  Even though hydroMazing monitors your pH and EC, I still recommend a handheld pH tester such as the Oakton EcoTestr pH 2 Waterproof pH Tester, which is excellent for the home gardener and has been proven time and again to be accurate.

The electrical conductivity (EC) of water estimates the total amount of solids dissolved in water, or TDS (Total Dissolved Solids). TDS is often measured in ppm (parts per million). In hydroponics, this measurement is used to determine the approximate concentration of nutrient solution to water. There are many hand-held EC devices available as well.

When do I need to adjust the pH?

Only under the following conditions:

pH is at or below 5.0 or above 6.5

AFTER at least 30 minutes from the time of topping-off or changing the nutrient solution.

How to adjust?  I highly recommend using pH Up and pH Down from General Hydroponics sparingly and only when necessary.


Flushing means to literally flush empty the nutrient solution from the hydroponics system and replace it with fresh “good” tap-water.  Then return the nutrient solution back to what it should be for the phase of growth.

When in doubt, flush the system and refresh the nutrients.  Otherwise, it’s recommended to flush your recirculating system every 7 – 14 days.  When I grow, I try to keep the nutrient solution working as long as possible, however, salts build-up over time and it is good to flush with fresh water from time to time.

What’s Next?

Using a Web Cam to Monitor Your Grow

Your Introduction to Hydroponics

When most people think of gardening, soil comes to mind. But plants don’t actually require it to survive. They mostly need the nutrients and minerals in the soil. Plants can grow in water, gravel, perlite, rice hulls, pine bark, cedar shavings, and other mediums, or even suspended in air.

The science of soilless gardening is called hydroponics. It may sound like something devised in a modern laboratory, but it’s been around for thousands of years. The essential ingredient is an oxygenated mineral-nutrient solution that’s circulated through plants’ roots.

Some scholars theorize the ancient Hanging Gardens of Babylon, one of the Seven Wonders of the World, was a hydroponic system. The Aztecs grew maize, squash, beans, amaranth, tomatoes, chili peppers, and flowers in high-output chinampas, or floating gardens, which were hydroponic systems. A traditional hydroponics system is still in use on Myanmar’s Inle Lake, and similar systems probably existed in ancient India, Greece, China, and Egypt.

In the early 1600s, the British scientist Sir Francis Bacon, father of the scientific method, conducted formal research on hydroponics, which he called “water culture.” Laboratory experiments continued into the 20th century. In 1937, William F. Gericke applied the experiments to large-scale commercial applications, and the modern hydroponics movement was born.

Today many people identify hydroponics with marijuana growers, who’ve made use of the technology. But much of the world’s greenhouse produce is now grown in hydroponics systems, including some of the lettuce, tomatoes, herbs, and veggies in many supermarkets’ refrigerated cases.

Why Hydroponics?

Growing food without dirt, earthworms, and, sometimes, sunshine may go against common ideas of where healthy food comes from. But hydroponics has taken off for good reason. It offers a number of benefits over traditional soil methods and it may even help solve some of the world’s growing problems.

Water Conservation

Agriculture currently uses 80 percent of the fresh water consumed in the U.S. and 60 percent of it worldwide. Meanwhile a water scarcity crisis currently plagues every continent, particularly arid regions such as the American West.

With a name like hydroponics, it seems soilless systems would use a lot of water. However, on average, hydroponic systems use 10 times less water than soil agriculture because they recirculate fluids and cut waste. In the hope that soilless agriculture will help prevent worldwide water wars in the next century, the National Nuclear Security Agency built a hydroponics greenhouse in New Mexico’s Sandia Laboratory to test the feasibility of growing forage crops for livestock with hydroponics.

Land Conservation

Water is not the only resource in short supply. Many countries, including Great Britain, may face a significant shortage of farmland in the next two decades. Some studies estimate crop yield must double by 2050 to meet projected demands, and scientists warn that will not happen if current trends continue. In the past we’ve cleared forests and grasslands to plant crops, with grave environmental consequences. What if there’s a better way?

Some futurists, including microbiologist Dickson Despommier, are convinced hydroponics is the answer. In soilless systems, roots don’t need to stretch out as much because they’re supplied with all the nutrients they need. Crop yields are typically higher and more stable, and artificial lighting makes year-round crops possible. It currently takes a land area the size of Virginia to produce food for New York City. Despommier envisions cities feeding themselves with vertical skyscraper greenhouses. “If vertical farming in urban centers becomes the norm,” Despommier says, “then one anticipated long-term benefit would be the gradual repair of many of the world’s damaged ecosystems through the systematic abandonment of farmland.”

Less Pesticide Use and Runoff Pollution

Agriculture is the leading cause of water quality problems in the U.S., and pesticides, including endocrine-disrupting atrazine, currently contaminate our watersheds and drinking water. Many hydroponic farmers use zero herbicides or pesticides, and any system with the potential to curb pesticide use is important. Because plants experience less stress and are fed optimally, they’re healthy enough to resist any pests able to enter the greenhouse. Alternatively, organic methods can control pest infestations. Weeds are not an issue with hydroponics, since they need soil to grow.

Food Safety

We’ve all gotten used to headlines about deadly E.coli outbreaks. Twenty-three percent of foodborne illness deaths and 46 percent of foodborne illnesses are linked to eating produce, according to the Center for Disease and Prevention. Soil polluted by livestock waste is often pinpointed as the cause.

Because hydroponic systems are sterile and don’t have soil to be contaminated, disease outbreaks are less likely, especially in clean, well-run systems. (However, hydroponics does not completely eliminate the risk of foodborne illness. Proper precautions are warranted.)

Lower Food Miles

An eat-local movement has erupted across the country. Local produce is usually more nutritious, since vitamin content is depleted by light, temperature, and time. Moreover, local food doesn’t require the expense and energy expenditure of long-distance trucking. But how can people grow food in dense urban centers or inhospitable climates? Hydroponics may be the answer.

Take Emory University for example. The lettuce the school used to serve in their cafeteria had been trucked 3,000 miles before the students ate it. Students built a hydroponics system and now greens are grown 10 feet from the salad bar.

A number of companies, including New York-based BrightFarms, grow tomatoes, greens, and herbs hydroponically on the roofs of grocery stores. The supermarkets sign a contract to partner with BrightFarms for ten years, and in exchange, they’re able to sell the freshest, just-picked produce and eliminate some of their transportation costs.

Emory’s experiment and the growing number of partnerships between hydroponics companies and supermarkets indicate soilless agriculture may provide more local food choices in the future.

Potential Downsides of Hydroponics

Any time people change conventional ways, especially those as embedded in our identities as food cultivation, controversy is inevitable. Hydroponics is no exception, and it does have some potential drawbacks that should be weighed with the benefits. (However, it’s important to evaluate it in the context of the industrialized agricultural system we currently have, rather than an idealized one.)

Scientists are increasingly aware of the importance of the microbiomes in our soil. “There are millions of organisms in a couple cubic centimeters of soil,” explains biologist Jeanne Romero-Severson, and we’ve been unable to grow 90 percent of them in the laboratory. Because we still don’t fully understand the relationships between plants and soil microbes, it remains questionable whether we can reproduce them in a hydroponics system. For that and related reasons, a coalition of organic farmers oppose the USDA’s decision to allow hydroponically grown produce to be certified organic.

Most hydroponic growers claim their greenhouse-grown veggies are as nutritious as, or more nutritious than, conventional veggies, although data is hard to come by. There’s a widespread perception that hydroponic veggies are tasteless or watery, although the evidence is mostly anecdotal. In one blind taste test, hydroponically grown lettuce was rated as just as tasty as conventional or organic varieties. More nutritional analysis and taste testing on a variety of crops would be informative.

Several other issues may make hydroponics challenging or undesirable for some growers:

  • It can be expensive. Growers, especially large-scale ones, must make an initial investment to buy pumps, pipes, basins, lights, air filters, and fans.
  • Systems are made of fabricated materials, which require resources to build and maintain.
  • Commercial nutrient solutions are often mined and produced in factories and they can be pricey.
  • Systems, especially those with artificial lighting, can use a lot of electricity.
  • Large systems require technical knowledge and careful monitoring.

Many of those challenges can be mitigated for small-scale home gardeners. Setting up a soilless system can be inexpensive and easy and it’s an excellent way to understand the principles and potentials of hydroponics.

DIY Hydroponics for the Home Gardener

The first and often most daunting decision for any gardener is what to grow. The best veggies to grow in any garden are the ones a person or family enjoys the most. But some plants tend to work better than others in small hydro-systems.

Which Fruits and Veggies Grow Best

A small herb garden is a great way to get started. But before diving in, it helps to understand the basic parts and six different types of hydroponics systems.

The Basic Parts of a Hydroponics System

Six Different Types of Hydroponics

With a little basic understanding, anyone can make a simple system. A passive wick system is the easiest to start with because it doesn’t require a pump, timer, or electricity. (For those not DIY-inclined, many companies offer hydroponic starter kits.)

How to Make a Hydroponic Wick System in a Jar

Tools needed:

  • Wide-mouth quart-sized jar
  • Small planting container (with drain holes in the bottom) that nests in the mouth of the jar. (A small, plastic planter with the following dimensions fits perfectly: 3.5 inches wide at top, 3.25 inches long.)
  • A clean sock, towel, or t-shirt cut into 9-inch by 1-inch strips. (One strip is needed for each drain hole in the planter.)
  • Tape
  • Water soluble nutrients
  • Distilled water
  • Growing medium. (Coconut coir, perlite, and clay balls are good options for beginners. All of them can be sterilized and reused. Purchase online or at a hydroponics store.)
  • Small herb transplant

System setup:

  1. Sterilize the jar and planting container by washing in soap, water, and diluted vinegar. Rinse well and dry.
  2. Using the distilled water, follow the directions on the nutrients to make some nutrient solution.
  3. Soak the strips of towel, T-shirt, or sock in the solution.
  4. Thread one strip of the soaked material through each drain hole. Temporarily tape them to the top of the planting container.
  5. Braid the strips hanging out the bottom of the container together so there’s one wick hanging down.
  6. Fill the planter midway with growing medium.
  7. Gently rinse the soil off the plant roots and transplant it into the growing medium, adding enough medium around the roots for support.
  8. Remove the tape that held the cloth strips to the top of the planter. Space them evenly around the plant roots. They will deliver the nutrient solution to the roots.
  9. Fill the jar halfway with nutrient solution.
  10. Nest the planter in the jar. The solution should be one to two inches beneath the level of the planter and the wick should hang into the solution.
  11. Put the system in a sunny window or under a grow light.
  12. Monitor, and add nutrient solution as needed.
  13. Every two weeks wash the jar and replace the nutrient solution. (Reuse old solution to water houseplants.)
  14. Enjoy fresh-grown herbs.

Hydroponics systems are already making food easier to grow in deserts and in land-starved countries like Japan where there are concerns about radiation-contaminated soil. If some futurists are correct, hydroponics could help solve impending food, water, and environmental crises. At the very least, soilless systems offer urban apartment dwellers and people living in inhospitable climates the ability to grow food, and that’s no small feat.

Don’t forget to check-out this handy IndoorGardeningChecklist – print yourself a copy!