My local "$2 shop" (Daiso) sells 3 test tubes and a rack for $2, ostensibly for plants. So I wanted to experiment whether I could 'rehome' my excess cuttings in these test tubes, and which species will adapt to 'test tube life' better.
I filled 3 test tubes up with fish tank water, slotted in unwanted plant cuttings and left them in the open where they got plenty of direct sunlight.
I would top up the water lost from evaporation with fish tank water but did not do any 'water change.' This is the result after 14 days.
The leftmost testtube (now replaced with a new Bacopa cutting) had a bit of algae because the cutting didn't adjust to the test tube well and was clearly dying. There is still some of the old algae left at the bottom, want to see if the algae spreads in the next 14 days. This 'result' is consistent with the wisdom in this forum that organic waste (eg: from dying plants) is a primary trigger of algae.
The middle and right test tubes (P. 'Sao Paolo') , there was good emersed growth, and hardly any algae. The dark green of the emersed leaves is consistent with the plant getting quite a bit of direct sunlight. I had expected 2 weeks of direct sunlight to at least result in some GSA spots on the test tube (the water came from my fish tank, so there are probably loads of algae spores in it) but there weren't any.