Your Second Transplant
Now that we understand what the Kratky method is, we can continue our hydroponics journey. The next step is to transplant our plants from the mason jars into larger totes. This should be done once the plants have outgrown the mason jars.
The totes I use are 25 liters in size, and I typically house 6 plants in each. This provides each plant with a little over 6 liters of space. Coming from a 500 ml mason jar, that’s about 12 times more space than the plant has been used to at this stage.
I use the same 2⅛-inch hole saw to drill holes in the lid of each 25-liter tote. At this stage, I recommend using black totes to help prevent algae growth. You can find suitable totes like the Sterilite 17-Gallon Black Totes.
Next, I insert a 2-inch PVC plumbing pipe into each hole. You can get the right type of pipe here: VENTRAL PVC Pipe Sch40 2 Inch (2.0).
Before inserting the pipe, use a smaller hole saw bit to drill several holes along the side of the pipe. These holes allow water from the tote to reach the plant roots.
To secure the pipe in place, apply aquarium silicone around the base of the pipe and the lid opening. It’s crucial to use aquarium silicone—not regular silicone—as it's the only kind that won’t leach harmful chemicals into your nutrient solution. I recommend this option: Aquarium-Safe Silicone Sealant.
Allow the silicone to cure for a day or two. Once it has fully dried, you can insert your plants into the tote system. The 2-inch pipe should fit snugly with your 55 mm net cups. This setup helps keep the root systems of your six plants relatively separate for quite a while. Eventually, a third and final transplant will be necessary, but the PVC pipe design will minimize root tangling between neighboring plants during this phase.