Aeroponic System Basics

Reader Contribution by Erik Thiel
1 / 7
2 / 7
3 / 7
4 / 7
5 / 7
6 / 7
7 / 7

Growing lettuce and other leafy greens indoors with an aeroponic system in a south-facing window in the basement seems like a wise move. Growing anything seems like a wise move, I suppose. However, the short days during this long winter has soil-growing 30-day Asian greens at only 2-inches in height, although they were sowed over 30 days ago.

I hope with the use of an aeroponic system, growing 30-day Asian greens can actually take somewhere around 30 days. However, I do not plan on using indoor lights to make this happen, just the south-facing window. Anything that makes the electricity bill go up is strictly forbidden at this time. Plus I don’t want passerby’s to see an indoor light and some dude with dread locks. I’ll have the neighbors, riff-rats, and cops thinking I’m up to something. Or worse – someone will break inside and steal my Asian greens!

For right now I will explain the most simple, basic steps to growing lettuce with an aeroponic system. First, we will go over what aeroponics is and what our goal is, then we’ll talk about the initial expenses, touch on pH and nutrient solution, and last, we will hope the sun provides enough life-giving rays long enough each day to grow these Asian greens in 30-days.

About Aeroponics and What I Want to Accomplish

Aeroponics, like hydroponics, deals with growing plants without using soil. Once soil is taken from the equation, all that is left is water, air, and nutrients. The air becomes the growing medium rather than the soil. It is then left to me to measure the nutrient solution, or the fertilizer being mixed into the water. The lid must be secure to block out all light from hitting the roots dangling inside the aeroponic system; therefore, the humidity will stay at 100 percent while oxygen-rich nutrient solution sprays the roots all day.

The aeroponic system is simple. Advanced Simplicity 202-type simple. It starts off as a tote. A PVC pipe is then added horizontally a few inches below the top of the tote. This PVC pipe will have spray-misters drilled into it and a tube coming out to the bottom of the tote to connect to the water pump. Then there is the lid to the tote. This is where the top of the plants grow above as the roots grow inside the tote. It will have holes cut out to install netted pots that will hold the hydro balls, also known as expanded clay. The hydro balls help to hold moisture, nutrients, and oxygen for the roots.

I germinate the seeds in rockwool cubes, then place the rockwool in the netted pot surrounded by hydro balls. The lid should also have a hole for the plug of the water pump to run out of and an extra and larger hole in the middle for taking water out to measure pH and nutrients. Remember, when growing indoors all water should be below the waist and everything electric above the waist. (Growing Indoors with Hippies 101.)

One claimed benefit to growing with hydroponics is plants grow faster because nutrients are available for the plant as fast as the plant can take them. Growing in soil minimizes the amount of oxygen available to the roots in comparison to hydroponics, which maximizes oxygen. In other words, soil holds the nutrients longer and acts as a buffer zone; whereas, nutrients in hydroponics are instantly available. Growing indoors with 600-Watt lights at vegetative intervals of 18-hours a day and flowering intervals of 12-hours a day is some crazy productive stuff. It’s also goes way past my budget and free time. (At least until Pennsylvania becomes the next Colorado.)

The major advantage to aeroponics versus hydroponics is the roots have the highest potential to absorb nutrients through the air. In hydroponics, the water runs through the roots at timed intervals, always draining back into a main water chamber. In aeroponics, the main water chamber is the only chamber and it’s a daily, steady combination of oxygen, water, nutrients, and roots.

The major con to hydroponics is if something goes wrong the plants are much less forgiving than if their roots were in soil. And in order for everything to run smooth the gardener needs to be on top of stuff. Water pH, temperature, and nutrient solutions need to be checked, water needs to be changed every week or two, spray misters cannot clog and do not forget, the garden is growing faster than soil; therefore, the gardener must be fast too. Aeroponics is even less forgiving than hydroponics. And more touchy.

With all that said, it’s simple. Especially when you start off with lettuce varieties and avoid fancy indoor light systems. (I admit, I admire.) And that is my goal. I just want to grow greens indoors with my aeroponic system. Simply.

Initial Expenses

To follow the flow of simplicity, let’s assume the aeroponic system is ready to go. It’s even filled up with water a few inches above the water pump and it’s plugged in with soaked rockwool cubes germinating seeds. In order for plants to grow, the water pH must be balanced and nutrients must be added to the water. Other than the system, some minor purchases would be for the hydro balls, water pH up/down solution, and nutrient solution. Then there are the major initial expenses. One is a pH meter to measure the pH in the water and two is a TDS meter to measure the nutrients in the water. Fortunately, they are affordable.

I went for the most affordable of each and when I called the pH meter cheap the dude from the hydro-store looked at me crazy. “It’s a great pH meter. It’s not that sophisticated because you’re only growing greens,” he made sure to say. Sounded great to me because I don’t want anything unless I absolutely need it. The pH meter I chose is a Hanna Champ HI98106 and the TDS meter is made by HM Digital, the TDS-3. Both were under 50 bucks and both have worked great, even now after sitting in the shed for 2 years.

Every now and then the meters will need to be calibrated to be sure all measurements are accurate. The pH meter requires more attention to that than the TDS meter does. It’s a mind-numbingly easy process and the calibration solution is cheap. Technically, you are supposed to pour a little calibration solution in a jar, use it once, and dispose of it. The dude at the hydro-store let me in on a little secret; he said, “Use it once, put a lid on it, and use it a second time. They say not to do it but you can get away with it.” My man.

Most soil gardeners will be familiar with pH. TDS, or total dissolved solids, may be foreign – it is used to measure nutrients in the water. Those same nutrients may also be measured under different scales that look like this: EC, DS, or CF. I say chickpea, you say chana and the can on the store shelf says garbanzo. But I just want a bean! (I also just lied, it’s much more complex. But remember, simple.) Here’s an explanation from Gardening Indoors with Soil and Hydroponics by George F. Van Patten:

Pure distilled water has no resistance and conducts no electrical current. When impurities are added to pure distilled water in the form of fertilizer salts, it conducts electricity. Nutrient (salt) concentrations are measured by their ability to conduct electricity through a solution. (Don’t worry, it gets easier.) Simple electronic meters measure this value and interpret it as total dissolved solids (TDS). The TDS meter gives me a reading in parts per million (PPM). I then just need to know what number to aim for in the ppm measurement to grow lettuce.

pH and Nutrient Solution

Let’s keep talking about nutrient solution. In order to grow lettuce with an aeroponic system all I purchased is General Hydroponics Flora Gro. What I like about the dude at the hydro-store is he only sells me exactly what he thinks I need. Flora Gro is part of General Hydroponics basic Flora Series which consists of Flora Gro, Flora Bloom, and Flora Micro. I do not need Flora Bloom because I’m not growing tomatoes or chickpeas or any other vegetable that fruits. The Flora Micro are micro-nutrients that plants may need. This is what he said about the Flora Micro knowing I was short on cash: “You can probably get away without using Flora Micro since you’re only growing greens.” I observed his wording carefully noting I may want to purchase it on my return trip when I buy more hydro balls. We’ll see. I admired his wording for not upselling me like a dude on the brink of starvation. (Technically, he has a building full of food.) With this figured out, all I need to know next is how much Flora Gro to add.

Different plants require different amounts of nutrients. For lettuce I need my TDS meter to measure around 800 ppm. According to this chart, lettuce grows best between 560 and 840 ppm. Technically, I’m growing Asian greens – mizuna and tatsoi. I’ll aim for 800 and increase if necessary.

pH is pH and it is fairly simple yet the numbers a soil gardener may be familiar with are different. In a hydroponic system, vegetables do best with a pH range between 5.5 and 6.5, and it is even better to aim between 5.8 and 6.0. According to the book by Van Patten, the pH of the nutrient solution controls the availability of ions that plants need to assimilate. According to me, it’s much easier to stick the pH meter in water and adjust it with pH down or pH up to aim between 5.8 and 6.0.

Because the water needs changed every week to two, (more often with massive root systems), it is required to run straight water through the system to flush it out between nutrient changes. If the water is not changed the plants can die – the major con.

Simplified Summary

I start off with fresh water and germinating seeds in rockwool placed in netted pots surrounded by hydro balls – water pump plugged in. I dip a little glass bowl into the water, add some pH down and some nutrient solution, a little at a time and pour the bowl back into the aeroponic system. Then I forget about it for the day. The next day (or the next) I take out more water, measure it with my pH meter, then with my TDS meter and add more depending on the measurements. It’s O.K. to gradually build up to 800 ppm because the plants are still seedlings. The pH I want to keep at 6.0 or a little below.

As for organic, I don’t know. According to General Hydroponics, only unrefined minerals can be certified organic and unrefined minerals do not dissolve well enough for hydroponic systems. Products such as their Flora Series comes from high-quality refined minerals which means they cannot be certified organic. But I’m not after certifications.

For right now, I just want to see if I can formulate growing lettuce with the aeroponic system into my weekly routine year round in the south-facing window in the basement. Ultimately, I feel a deep connection with the soil and sun versus liquid nutrients and indoor lights, but I do enjoy each trip to the local hydroponic store where the owner is growing a ton of veggies all over the place. And selling weekly shares. Perhaps one day, we can take a trip. Until then, stay tuned to check out my progress.