I really like this idea. We already use a version where we grow plants lacking certain nutrients (without phosphate, without nitrate, etc), but for a STEM session or science at home, this might be far easier to come to grips with. In the experiment Lemon and Lime did, they used tap water, river water, salt water, carbonated water and soda. I would love to add in acidic and an alkali water (both can be made easily at home).
Then, measure the plants and their growth over a week or two – obviously at home that is far easier to do each day and in STEM the changes might be huge within a week, but I still think it would be so fun to do! Plus, we sometimes have an issue with getting our STEM members to make predictions and they do it during/after the experiment (you know, when they can’t be wrong! Haha!) and this one is ideal because they won’t see any results for a week!
I think it might also be far more visual than the in-school version that we do! It might also be worth trying in test tubes with cress seeds as the watering them aspect is never as much of an issue and the growth is far quicker.