James has asked a few questions that I thought would be beter explained as a blog.
Kratky hydroponics is based on providing a plant with the nutrients and water it needs till harvest, in 1 container. No maintenance and cheap with no equipment. There are many expansions and methods around the idea and the system is easily modified.
The basic idea is the seed is placed in a grow medium, the roots grow down and use the liquid nutrient and the plant grows out the top of the container. The roots use the water creating an air gap and air roots grow here, the water roots follow the water down. By the time the nutrients are used, the plant is ended it's harvest life.
Now, a light proof bottle prevents algea growth. Air bubbles or circulation can also help, but are not needed. Experiments have also shown that the algea does not affect plant growth, just look ugly.
Nutrients can be topped up so calculations are not needed making it even simpler. There are various types of powders, liquids and mineral supplements to specialise, there also single products specialising for various plant types. There are chemical and organic options.
Volume of nutrients are more stable in temperature changes.
My choices are a chemical nutrient, nothing bad, food grade but not organic. This keeps 1 product to keep simple and cheap. Everything else in my garden is as organic as I can, I am also growing lettuce organically.
The container is clear, this was because I had a choice of clear or clear. So I chose clear. 😂 I do know I will get algea but I am OK with that. I did not want a dark colour that will heat up in the sun, as lettuce likes it cooler. The 34 l container will also be slower to heat up. Maybe I will add ice blocks if too warm😊. The only issue with the size is 34kg of flat liquid is heavy and awkward, moving liquid splashes everywhere, so is not as mobile friendly as I wanted.
Sunlight in this spot is limited to morning light up to mid day. So 6 odd hours in summer. More than enough for lettuce and no harsh afternoon sun.
Have a look on you tube, there are so many variations of this system.
Ask away in the comments. I am no expert, just a well read learner😂 but will asswer if I can.