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!

Hydroponics 101.1 Chemical Nutrients


We talk about hydroponics and aquaponics around here like it’s NBD. Jolene suggested that I do a hydroponics and an aquaponics 101 for the classroom for those of you who are new to this gardening technique. Hydroponics provides a great opportunity for hands on, authentic learning in the classroom. Since hydroponics deals with nutrients only and aquaponics deals with fish, I will start with the less complex of the two: hydroponics. We’ll first take a look at the nutrients used in hydroponics. Further posts will describe the procedures you can use to set up a hydroponics system in your classroom. After we describe the hydroponics system we will move to the aquaponics system for your classroom. Yes, it is possible to do both in the confines of a single classroom!


Hydroponics is the use of chemical nutrients to grow plants in a medium that does not contain soil. The nutrients used in a hydroponics system contain the typical N-P-K (Nitrogen, Phosphorus, and Potassium) that we are taught that all plants need for growth. But the nutrients also contain numerous micro-nutrients needed for healthy plant growth. If you think that you can use the fertilizers from a garden center, think again, fertilizers like Miracle Grow are not suited to hydroponics because they lack the micro-nutrients. So while your plants may grow, they will not do as well as if you used the proper nutrients for a hydroponic system. But don’t fret, I’m now going to tell you where and how to get these nutrients very inexpensively!

Nutrients PH-Down

The three nutrients I have used are Epsom salt (Walgreens), calcium nitrate 15.5-0-0
(Amazon) and Tomato 4-18-38 (Amazon). You should also be concerned about the pH of your water. Where I live, in Wisconsin, our pH is about 8.0. Plants like a pH of about 6.5-7.0, so I use a chemical called pH down in my hydroponics tank which holds about 25 gallons (Brew and Grow).


If you have children growing individual plants and your water is alkaline, I have them add a drop of lemon juice to each of the containers every day or two.Hydroponics-101a

Watch for hydroponics 101.2 methods in a future blog post.

Maker Monday: When Life Gives you Lemons…Make a Fire?

Do you remember when I told you that my family is crazy…I mean full of creativity and collaboration? We often spur each other on to try new things. To be curious. To work hard on solving problems. To dig for answers. Well, my dad’s birthday rolled around and we had a family party that involved lemons. Zinc nails. Copper nails. Wire. And fire. Well…let’s not get ahead of ourselves. The question: Can you really start a fire from a lemon?


Spreading like wildfire {ha! pun intended!} around social media was a video of NorthSurvival (as it turns out this is a hoax! He makes advertising money from this video.). NorthSurvival demonstrates how to use a lemon and some other odds and ends to start a fire. My sister, Amanda, showed up to the birthday party with a bag full of fun to test this method out. She and her family had started the experiment earlier in the day but couldn’t get it to work, so she brought in more of the {crazies} family members to give it a whirl.

First you’ll need a lemon, zinc nails, copper or brass nails or brads, wire, insulated wire, toilet paper, and steel wool. I know. You’re already wondering how you’re going to find these items when you’re in a desperate survival situation. Trust me, you’re not going to need them. You’ll be better off digging up a battery and giving it a shot. {Side note: I haven’t tried the battery trick yet, but when I do, you’ll be the first to see my results!}

Lemon Lemon1

You can watch the video for the details on how to build it.

We tried. And we tried. And we tried some more. We switched out the copper nails with brass brads (because it looked like that might be what he was using). We tried different wire, different conductors, longer wire, shorter wire, more toilet paper and steel wool, less steel wool and toilet paper. We tried using a new lemon. We rotated through the family. It sat on the table and family members hovered over this mess for hours trying to ignite the toilet paper. We did measure 0.5 volts using a voltmeter, but it wasn’t nearly enough to get a fire started.


After hours of work on this, I finally decided to turn to the trusty internet I scoured websites looking for people who were successful in this method. I found not a single person who had tried it and reported failure. I read comments. I read websites. I found one website that listed it on the very bottom of ways to start a fire…but I don’t think they actually tried it.

And then Mrs. Brainiac on the hunt finally found a video explaining that NorthSurvival was a hoax! See the video below. Next time we’ll light the birthday candles with matches.

If you want to try an easy hands-on project using electricity that actually works, check out our Light Up 3D Washington Monument! There’s no hoax here!

Friday Follies: Lego Love

Legos®. Those colorful, creative little bricks that kids love to tinker with. It takes grit and persistence to build a project out of these little guys. It’s all the stuff kids enjoy. Problem solving, trial and error, risk taking. They use their own special engineering design process, they make mistakes, have failures that set them back and then, success! Tada! You made a robot. Or a tractor. Or something that looks awesome even though I have no idea what it is. The important thing is that you know what it is. And what it does.

It’s Mrs. Brainiac back for some Friday Fun! Today, she will share some Lego® love. Note that Jerry Brainiac loves Legos®, Mrs. Brainiac’s relationship with Legos® is ambivalent.

The most fun thing about creating with Legos® is actually a secret. A secret that only adults know. The odds of a budding Lego engineer reading this blog are slim to none so I feel confident I can reveal that secret here. Ready? Kids don’t know that when they are having fun with Legos® it’s actually a learning experience. Yes, just like school. And kids like learning. And math. And science. Yes, kids like math and science if it masquerades as fun.

Kids don’t know that it takes grit and persistence to build a project out of Legos®. They don’t know they are using problem solving, trial and error, risk taking. They don’t know they are using an engineering design process.  They don’t even realize that they’re making mistakes, learning from them and that’s why they successfully complete a project. They think they are just “playing with Legos®.”

Bonus “fun” is making a robot out of Legos® and then programming it to function. Make it go frontward and backward or speed up or turn. When a kid has “fun” programming Legos®, it’s possible that when that kid grows up, he or she might get a “fun” job programming computers. And that’s the secret some adults don’t know. You can have fun at work if you do something you enjoy that challenges you and offers variety and keeps your brain exercising.

But Legos® aren’t always fun. Jerry Brainiac has thousands of Legos. These Legos are all over Mrs. Brainiac’s house. Mrs. Brainiac doesn’t wear shoes in the house. You see where this is going.

Sometimes Mrs. Brainiac helps Jerry Brainiac at school events. Hundreds of kids attend and they learn to make and program Lego® robots. Thousands of Legos® and hundreds of kids. Kids with colds during the winter. Billions of germs on the thousands of Legos®. Mrs. Brainiac didn’t have Legos® when she was a little girl and doesn’t understand the attraction. All she thinks about are the germs. But she helps the kids anyway. Sometimes the kids have to show Mrs. Brainiac how to put them together right. And that’s good because you retain more information when you teach it to others. So teaching Mrs. Brainiac how to build Legos® helps you retain information. You’re welcome, kids.

Now let’s program the Lego® robots. The program uses pictures instead of words so kids that don’t read well can still do great programming. Once a little boy fresh from China was visiting and he picked up programming right away even though he didn’t know any English at all. So if a child is struggling with reading or language barriers, gaining some success and confidence from programming Legos® can be a good thing.

Computer Programmer!

Computer Programmer!

If Mrs. Brainiac can find educational value in Legos® then EVERYONE should be able to. So, get the kids going and have some fun with Legos®.  Your brain will thank you. And when your child grows up to be an engineer, you may thank Mrs. Brainiac for sacrificing the soles of her feet to the Lego® brick gods.