Lessons In Hydroponics

By Sara Elliott
Published: September 1, 2015 | Last updated: April 26, 2021 11:32:03
Key Takeaways

From ways to stretch a dollar when it comes to your lighting system, to effectively monitoring your pH levels, to scaling up your hydro system, the following article highlights many things every hydroponic gardening newbie should know. These lessons in hydroponics are things many growers have had to learn the hard way.

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The hydroponics industry is alive and well, putting down roots in desert landscapes, in underwater greenhouses and even in the frozen tundra of the Arctic Circle. Spurred by concerns about food safety, and by a growing focus on finding newer, better ways to feed the burgeoning human population, soilless growing is becoming the darling child of modern agriculture.


For the hobbyist just starting out, that’s both good news and bad news. Hydroponic gardens are springing up on patios, in basements, in garages and in backyards. Hydroponic pioneers are braving the congestion and pollution of the big city and nestling comfortably into suburban settings. All of this interest means innovation as well as mass production, which translates to lots of different products on the market available at attractive prices.

If you’re just starting out, how do you begin to sort through all the options? Even things you’d think would be simple can involve complicated computations and an alphabet soup of acronyms. All of these unknowns may see some newbies running back outdoors to their secure, humus-rich veggie patches to spend summers watching the skies instead of their EC meters. Instead of giving up, though, check out the following common sense suggestions about hydroponic gardening, most of which have all been figured out the hard way.


Grow Lighting Tips

Artificial lighting is a big theme in hydroponics. It’s no wonder—plants use energy from sunlight to produce their own food and maintain essential functions. Poor lighting kills plants faster than almost any other type of deficiency. When you garden outdoors, nature does the heavy lifting for you by providing full-spectrum, diffused light.

When trying to re-create that abundant light source, you have to make some practical considerations. It isn’t just a matter of choosing fixtures and bulbs that provide enough light. That would be almost as simple as picking a sunny spot in your garden to grow tomatoes! For starters, use a basic formula to ensure adequate illumination for your plants. For leafy greens and low-light plants, allow at least 25 W of light for each square foot of growing space. For sun-loving plants, increase the amount of light to around 40 W per square foot of growing space.

There’s a lot more to it than that, though. Hydroponic lamps are available in light wavelengths that approximate full-spectrum light or only certain portions of the light spectrum, typically the blues and reds preferred by plants as opposed to the greenish-yellow wavelengths human eyes are sensitive to.


The type of illumination a grow light produces may be more suited to different plants or different phases in a plant’s life cycle. Cool or blue-spectrum light (430-450 nm) encourages leaf, root and stem development, while red-spectrum light (640-680 nm) enhances flowering and fruiting. Metal halide (MH) lights are popular for vegetative growth, and high pressure sodium (HPS) lights are a popular choice for the flowering cycle of most plants.

So, why doesn’t everyone just use full-spectrum lights? Newer lighting technologies like LEDs tend to solve some classic artificial lighting problems, like light-spectrum limitations, high heat output, limited bulb longevity and high energy costs. These lights also tend to be expensive and out of the reach of many growers just starting out.


Whatever your budget happens to be, you’ll discover most plant lighting options come with tradeoffs. Here’s a good example: Switchable magnetic ballasts can run either MH or high HPS bulbs, making them sound like the most flexible and convenient lights available. However, magnetic ballasts are wattage-specific and can produce quite a bit of heat when compared to electronic ballasts.

They are also quite a bit heavier, which means they aren’t suitable for every situation. Pay a little more and you can find fixtures that include both MH and HPS lights in a single unit. The lesson here is to recognize any limitations in the light technology you’re buying. Managing any limitations will likely inform some of your other choices.

Ways to Maximize Your Growroom Lighting

Lights vary in intensity, how effectively they diffuse illumination, the amount of energy they use, and the amount of heat they generate. Because lighting constitutes one of the biggest startup and operating costs for an indoor garden, manufacturers and users have come up with some ingenious ways to stretch a dollar. Check ‘em out:

  • Pair lights with reflectors that make the most efficient use of illumination by directing it downward. Reflectors outfitted with cooling technology may also save on the cost of fans and other accessories. Again, it’s a balancing act. Your first system will probably take you through at least a couple of seasons before you upgrade. Grab a sharp pencil and compare the cost of accessory options.
  • Consider using an enclosure like a grow tent, or adding silver Mylar sheets to your set-up. They will reflect light below the canopy to reduce waste and help plants grow more evenly.
  • Deploy grow lights during the overnight hours. Many utility companies charge lower rates during off-peak times. In addition, evening temperatures are usually cooler than daytime temperatures, which may help if you’re working with hot lights in an enclosed space.
  • Add a light-moving system if you have a large set-up. Doing so will maximize your light distribution and reduce heat buildup. Light movers can help you avoid having to buy additional fixtures.

Before we leave the topic of grow lights, it’s only fair to mention that the quest for effective, cool, energy-efficient lighting is at the forefront of indoor gardening research. A product that seems out of reach today will come down in price—maybe by the time you’re ready to upgrade. For now, if you find the topic of indoor plant lighting too overwhelming, high intensity discharge (HID) lights are the most popular on the market. For small-scale, hobby-based applications, 400- and 600-W sizes are often recommended.

Lessons in pH

If you’ve gardened outdoors or kept houseplants, you’ve dealt with pH before. It’s the potential of hydrogen scale that measures acidity and alkalinity from 1 (most acidic) to 14 (most alkaline), with 7 being neutral. It’s easy to misjudge how important pH is in a hydroponic system. In a soil garden, a plant may have a broader pH tolerance than it would when grown hydroponically.

This has to do with one of the basic tenants of soilless growing: the reliance on dissolved nutrients. Remember, plants grown hydroponically can’t forage for what they need. They are completely reliant on liquid nutrients dissolved in water. The problem is that the constituents of a nutrient blend are only soluble (dissolved) within a narrow range of pH, around 5.8-6.8 depending on the element involved.

Think of it as the Goldilocks zone. Outside this zone, minerals will begin to precipitate out of solution. You can actually see them as little particles accumulating in the nutrient reservoir or on the system’s fittings. This can happen quickly because a number of things, like poor nutrient circulation or changes in nutrient density as plants take up water, can have a marked impact on pH. Most hydroponic primers recommend checking nutrient pH regularly and adjusting it as needed.

There are basically three types of testing equipment to choose from: paper strips, liquid testers and instant-read meters. Any one of these three meters will do the job, but paper strips may be tricky to read at first because the color gradations that distinguish different values can be hard to tell apart. For ease of use and to discourage delays in testing instant read meters are convenient and won’t break the bank. They can be finicky, though. Look for a brand that’s waterproof and calibrate it often.

Lessons in Nutrient Monitoring

A pH meter is just one useful monitoring tool that will help you keep track of what’s going on with your hydroponic nutrient mixture. Just as important, and infinitely more confusing, are EC and TDS meters. These tools allow you to monitor nutrient concentrations in the liquid you’re feeding your plants. Like pH, nutrient concentration, which is measured in parts per million (ppm), can fluctuate in the dynamic environment of a hydroponic system. Too few nutrients and plants go hungry; too many, and they begin to sustain damage from over-fertilization. This can result in yellow leaves, singed leaves, stunted growth and defoliation.

A basic hydroponic food contains about 20 nutrients plants need to grow. Concentrations of these important ingredients aren’t detectable through a visual inspection, but they can still be evaluated. There are two types of useful meter readings when determining nutrient concentrations. This is important to note because nutrient manufacturers will sometimes prefer one measurement or the other in their instructions and guidelines.

TDS – A TDS reading reflects the amount of total dissolved solids in the water as parts per million (ppm). It doesn’t include suspended particulates, not even small ones. It measures dissolved elements like iron, potassium and magnesium. If you put a batch of prepared nutrients in a container outside on a sunny day and let all the pure water evaporate, the mineral salts and other dissolved elements will remain as a powdery residue. This is what’s being measured when you’re using a TDS meter.

EC – An EC (electrical conductivity) reading is another way to get the same information as a TDS meter. Most elements other than hydrogen and oxygen conduct at least a tiny amount of measureable electricity. Pure water doesn’t conduct electricity, but a dissolved solid does, so measuring the electrical conductivity in a water mixture will reveal the amount of dissolved solids or impurities it contains.

Bonus Tip: A TDS meter isn’t a perfect tool. It doesn’t evaporate any water to analyze the residual solids. It makes a guesstimate based on—wait for it—electrical conductivity. The data may be expressed differently, but the methods for acquiring the basic information for ppm, TDS and EC are all pretty much the same.

Choosing a meter to help you determine the nutrient concentration in your reservoir is easier than it used to be. Today you can find inexpensive combination meters that give you both EC and TDS readings. For the best results, choose meters that are waterproof, easy to read and easy to calibrate.

Lessons in System Size

Many seasoned indoor hydroponic gardeners say they wish they had planned bigger right from the start. Starting small with your hydroponic garden sounds like a sensible approach, but it might not be the best option.

Problems with bacterial growth, nutrient balance and pH swings can go from bad to worse more quickly in a smaller hydroponic set-up than in a somewhat larger one. The same principle goes for the potential for dangerous temperature fluctuations and other lighting problems. In a larger ecosystem, negative changes occur more slowly, so there’s more time to adapt. Extra resources also make it easier to refine one’s interests, learn and improve.

Lessons in DIY Hydroponics

If you’re thinking of building your own hydro system, there can be problems with a strictly DIY approach, regardless of its size. Cobbling together a DIY system will teach you the basics fast, but at a cost. It’s a challenge getting everything to work right on the first try, and the learning curve can be a steep, expensive one.

Depending on your budget, it might be better to invest in a bundled system that can sustain a number of plants. Integrated components designed to work well together take the guesswork and some of the potential stresses out of making a great start at hydroponic gardening.

Many introductory systems also include automation tools like timers that make it easy for you to concentrate more on your plants than on the technology that supports them. Give the style of your system the most thought before you take the next step.


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Written by Sara Elliott | Gardener, Writer

Profile Picture of Sara Elliott
Sara Elliott is a professional writer with extensive horticultural knowledge acquired through theoretical study and practical experience. You can find her gardening and lifestyle pieces in print and online.

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