For a betta tank, I really wouldn't recommend no tech. At the very least, bettas need a heater and a filter, which means fairly stable temps, making them unsuitable to be solar powered. The sunlight, even indirect sunlight can have a pretty strong effect on the temps in these small containers, which as you get smaller, the effect becomes more extreme.
There is also pretty low bio limit on what these jars can sustain. With a no-tech like my jar, a single shrimp and a bunch of snails is all I feel comfortable putting in there. You'd need a lot of fast growing plants to keep up with the waste production of the fish, not to mention the regular water changes.
Really it's a good looking bowl, and plant wise it looks fairly good (keep the leaves of the bamboo above the water), but I just wouldn't have a fish in one of these.