It's time for Part 3 of our DIY Kratky Container Series! In this installment, we'll focus on preparing your recycled containers to hold the nutrient solution for your growing plants. We'll also create a handy seed-starting dome to boost germination success.

Preparing Your Nutrient Solution Containers and Seed Dome

For this part, you'll need two 4-liter water bottles with their labels removed. We're going to create two different sizes of nutrient solution containers: a smaller one ideal for seed starting (which will also hold our dome), and a larger one for more mature plants. This allows you to maximize your space as you cultivate plants at different stages, from germination to harvest.

Making the Small Nutrient Solution Container and Seed Dome 

To begin, you'll prepare the smaller container, which will also provide the dome for your seeds.

First Cut: Separating the Top for the Dome

Locate the black line we've marked on your bottle. This is where you'll make your first cut to separate the top from the bottom. The top portion of the bottle will become your seed-starting dome. Set this aside for now; we'll use it later when we assemble everything. The bottom portion of the bottle will be used to make your nutrient solution container.

1. Identifying Ridges and Guidelines You'll notice that most water bottles have similar ridges, regardless of brand or color. These ridges, along with faint vertical lines running from top to bottom, are our guides. You should also see breaks in the ridges that are evenly spaced. Look for the separate ridge lines and create four evenly spaced sections around the top of the bottle, we placed a line so you can see the start. We've also placed a black line on the bottom of the top ridge; do not cut past this point when making your tabs.

2. Creating the Tabs. These four tabs will help secure the top housing and prevent light from reaching the nutrient solution (which we'll cover in Part 4). To create the tabs:

   • Cut downwards from the top of the container to the next ridge line, making sure not to cut any further.

   • For each tab, make a cut approximately 1/2 inch from the center on both sides of the tab.

   • To ensure even spacing, you can use the faint vertical lines on the bottle. Place a small mark on the closest separated space. You'll find that cutting at every other separated space will give you ideal spacing for your four tabs. Don't worry too much about the exact width of the tabs; they just need to be wide enough to push through the slits we'll make in the pie plate in Part 4.

3. Connecting the Tab Cuts. Once you've made the individual tab cuts, your next step is to connect them. From the side view, you'll see where you made the cuts down to the top of the first ridge. Now, cut from one side of a tab to the start of the next tab, ensuring you do not cut past the start of the adjacent tab. Repeat this for each tab.

After making all the cuts, you'll have four long, thin tabs sticking up from the bottom of your container. Some growers might choose to cut to the second ridge line for a shallower nutrient solution container, which can reduce the amount of paint needed if you plan to paint it. However, for getting started, the depth from the first ridge is perfectly fine.

Making the Large Nutrient Solution Container

The process for making the larger container is very similar, with one key difference:

• Separating the Top: For the larger container, you'll separate the top from the bottom at the topmost ridge line.

• Creating the Tabs: You'll create the tabs using the very first and fainter ridge line, making sure not to cut past that line. You'll notice this ridge runs all the way around the bottle without separations. To create evenly spaced tabs, look down to where you can see the separated sections from the previous bottle. Once the tabs are made, you'll see that the only real difference between the two containers is their depth.

Stay tuned for Part 4, where we'll show you how to create the top of your container, which will also hold the base housing for your growing medium.