Aquaponics 101


I’m assisting Oconomowoc High School with the aquaponics system in their greenhouse. So far we have set up two systems with 50 tilapia in one tank and 50 perch in a second tank. We are facing some challenges with our systems from the heat that is building when the outside temperature reaches 70 degrees or above. Tilapia need a water temperature of about 80 degrees, while perch need a water temperature of about 70 degrees. Our greenhouse reaches over 90 degrees and can see temperatures of 110. Before the weather gets too warm we need to find a way to keep the water cool enough for the fish to survive. Enter Travis. Travis is a second shift custodian at the high school and has significant experience in building aquaponics systems. I sat down with him over lunch the other day and was very impressed by his knowledge and experience. Travis has a high school diploma but has so much knowledge that I thought he had a college degree. Travis has had much hands on experience fabricating and problem solving over 150 aquaponic systems. I asked Travis if he had a degree. His response was that he just had a high school diploma but he picked up a lot of money and expertise doing side aquaponics jobs. He also has sought out many experts and used collaboration to build his knowledge.

Our discussion just reinforced my belief that we need more individuals with the ability to fabricate, and to use their hands to build projects that solve problems. I’m very impressed by his ability to think out of the box. After about an hour of talking, we had a solution to our overheating problem. It struck me that what Travis is doing is just the thing I want my students to do. Think out of the box, collaborate, seek expert advice, problem solve. The world could use more people like Travis!

Hydroponics 101.4: Light Requirements


I’ve been growing plants using hydroponics for a few years now, both at home and in the classroom. For the first several years of doing hydroponics and aquaponics systems, I used a bank of T-5 fluorescent bulbs and they worked okay. But in this last planting, which I have set up in my basement, I purchased a bank of LED lights. I am passionately green and I read that LEDs are much more energy efficient and last much longer than any other type of bulb. I also read that LEDs can be tailored to provide the exact wavelengths of light for plants and flowers. You see, plants love light from the blue and red ends of the spectrum. While fluorescents provide some of that light, much of a fluorescent’s light is white and that is a waste of energy because plants use very little white light.

We’re currently in a series exploring Hydroponics {read our previous entries 101.1, 101.2, 101.3}.

The bank of LEDs was about $275 dollars. This was comparable to the cost of a T-5 bank of fluorescent bulbs, but I was astounded at the small size of the LED bank!


I was blown away by the light though! What the LED bank lacked in size, it more than made up for in intensity. The instructions stated that the light should be hung at least 24 inches above the plants. I was able to hang it at about 22 inches. I was stunned that the light covered an area of about 2×4 feet where the plants were located. This from a bank of lights that is five inches wide and 18 inches long! My fluorescent bank was 22 inches wide and 46 inches long.

I left the light on while I worked in the basement. After about 15 minutes I started to see everything in a green aura. The intensity and wavelength of the light was affecting my vision. I decided to turn off the light and construct an enclosure around my plants that had Mylar reflective material on the sides to reflect the light back on to the plants.


My plants are now bathed in blue and red light and are growing wonderfully.

Oh, and my vision is back to normal.

Hydroponics 101.3: The Circulation Method


Picking up where we left off in our Hydroponics series… The circulation method of hydroponics is ideal for you if you have a few more dollars to spend (as compared to the more limited Kratky Method) and you would like your students to make a hydroponic system in the classroom. It is a great way to integrate the engineering design process and STEM into your curriculum as well as offer authentic learning to your class. It also offers you a way of integrating principles of chemistry and physics into your curriculum.


We’re currently in a series exploring Hydroponics and Aquaponics.
{Read the previous entries here Hydroponics 101.1 and Hydroponics 101.2}


In the circulation method, you need to provide a nutrient trough for the plants to bathe their roots in. This can be done in many ways. Two methods that I have worked with are a floating bed system and a rail system. With both systems I had great success.


With the floating bed system, have your students construct a sturdy box of 2×4 lumber about two feet wide and four feet long. Attach a piece of plywood on the bottom and drill a hole for a bulkhead attachment to allow water to drain from the bed to a reservoir below the bed. Next, place a rubber pond liner inside the box and cut a small hole in the liner to match up with the hole you drilled earlier. Screw down the bulkhead and tighten it so that water will not leak out of the box. Now cut 2 inch holes into a piece of ½ inch thick pink Styrofoam insulation board. I used a 2 inch circular hole saw in a drill bit and ran the drill BACKWARDS so that the Styrofoam was not shredded.


Now you are ready to fill the reservoir with water. I use a large plastic container (about 25 gallons) with a small aquaponics pump on the bottom and a hose running up to my growing bed. I fill the reservoir with water, add my nutrient solution, turn on the pump and circulate the water. Monitor the water height in the bed so that when you add your plant cups their roots are touching the water. I also would recommend you add a PVC pipe below by attaching it to the bulkhead with a PVC fitting so that water flows back to the reservoir.

Next we’ll explore light requirements, planting and monitoring your system.

Adding Tilapia to our High School Classroom Hydroponics System

Last Friday I spent much of my day with five high school students on a field trip to a tilapia farm to pick up the tilapia for our aquaponics project. We purchased 50 tilapia from R&D Fish Farm in Oshkosh, WI. The students spoke with one of the owners and garnered knowledge from an expert who has been raising fish for 12 years. It demonstrated to me how passion can impact learning. Each of these kids gave up their day off of school in order to make this trip. It was an opportunity for them to learn and interact about something they were interested in. Learning in this way fuels a student’s curiosity and give meaning to learning in an authentic way.


We returned to the high school’s greenhouse and spent another hour acclimating the fish to the temperature and pH of their new tank. From each day forward, these students will need to monitor the pH, temperature, ammonia, nitrites and nitrates in the tank which contains about 175 gallons of water. In addition to monitoring water quality, the fish will need to be fed five to six times per day. A challenge that will face the students in the very near future will be how to hold the water temperature at 80 degrees since the tank is in a greenhouse that can reach temperatures near 100 degrees.


The second tank that is fish ready will be for perch that we will buy this coming weekend. Perch need to be held in a tank with a water temperature of about 70 degrees. These kids face many challenges in the near future in keeping these fish alive. These challenges will require them to use creativity to come up with solutions. Mistakes will be made but they will learn and adapt to keep this project going. It is a joy as a teacher to work in a meaningful environment where the goal in not just to pass a test.

If you want to try hydroponics but aren’t ready to take the plunge in a large system, download our Windowsill Hydroponics guide. We give you step by step instructions with photos that make it easy to follow and use for personal use, homeschooling, or in your classroom.

Hydroponics 101.2: The Kratky Method


Hydroponics gives your students an opportunity for hands on, authentic learning that is novel, STEM related and gives them a chance to tinker. We’re currently exploring Hydroponics and Aquaponics in a blog series (read Hydroponics 101.1).

Choosing the container that you wish to use for your hydroponic system is crucial. There are two ways that you can approach this. You can either place your plant in a container that has no water and nutrient movement which is Kratky method) or you can re-circulate the water continuously using a pump and aerator. Which method you choose depends on your space and budget.


With either method, you should begin your plants two to three weeks before transplanting them into your hydroponic system.

In the Kratky method you mix your nutrients in water and fill a container. Next, you prevent light from shining on the solution by duct taping or painting the container, then you cut a hole in the top of the container for your plant basket and you set the plant into the container with some of the roots not immersed in the liquid so they can get oxygen from the air. The upside is that you can grow lettuce and quick maturing plants in about 30 days. The downside is that the nutrient solution will run out or will begin to smell after about a month because no aeration of the solution takes place. This method is simple.

It is very important not to let light hit the solution or algae will begin to grow and use up all of the nutrients meant for your plant. This method is great for windowsill gardens or in small spaces that receive sunlight most of the day.


I’ve noticed some differences with each method. First, root development is much greater in the circulation method and plants do grow a bit larger (see photo comparison). Secondly, the nutrient solution can be used for a longer period of time due to aeration. I have eaten my lettuce from both systems and both salads tasted very good.

Next week I will tackle a circulating system. But before then we’ll be posting on adding fish to our high school aquaponics system!

Theory Thursday: Aquaponics Helping to Promote Student Engagement

photo (13)


I am volunteering about three hours per week at our local high school and setting up an aquaponics system with their FFA group. I spoke with the teacher, Marge, after class today and she complemented me on how much more on task the boys in the group are since we began the project. Marge said even the district administrator has noticed a difference. I don’t think that it is me, but rather the philosophy of learning by doing. Any time you give kids a task that has them learning hands-on it becomes much more engaging.

If you want to promote STEM or STEAM, allow kids to DO the work of science.

Sure, we have made mistakes and we have had fits and restarts in building the aquaponics tank structure and leveling it, but with each mistake and restart they have gained experience and knowledge. The class is learning about pH, ammonia concentration, nitrite and nitrate production by various bacteria and how to be careful with an ecosystem. Even adding treated city water to the system can change the  bacterial count.

It is nice to see the enthusiasm shown by the kids in taking charge of the project. We are currently cycling the water to produce nitrates from nitrites by adding ammonia to the system. This prepares the system for the arrival of our 100 tilapia in two weeks. By growing bacteria in the system, it will be ready for fish (that will produce ammonia in the form of urine).

Our system has two 175 gallon tanks that are connected by a siphon. The water from the two tanks is pumped into two grow beds filled with Hydrocorn clay pellets that filter out the fish solids. These two beds have just been planted with over 150 lettuce plants. We are also adding a floating bed of about 28 square feet. Watch for more updates!