I was about to take a swig from my large flask of filtered water (these Brita flasks have a filtering system as their top), which I keep by my window, when suddenly I noticed a green sheen at the bottom, an unexpected foldscope problem. I drained all the water and scraped the sheen out with a qtip and suspended the green stuff in a drop of water on a slide and covered it with a glass coverslip and taped the sides with cellophane tape.

Under the 140x lens, (low power), I noticed tiny oval cells, but the green color was only seen in the clumps.

And so I put it under the high power lens, 400x. It showed a single type of cell, a eukaryotic alga in all likelihood, but I felt frustrated about not seeing the source of the green and so… I tried and tried to bend and twist the foldscope,since that is often an easy way to align the LED with the condenser if it is mis-aligned. For once the blue light that came through wasnt what I wanted and so I started reading about how the white LED is actually a blue LED with a fluorescent substance that makes it white. Why the inventors of the blue LED got the Nobel prize (and deservedly), all this didnt solve my problem though.

In the meantime, a strange phenomenon emerged, there were bubbles in my field and they were everywhere (about 45 minutes after making the sample). After some juggling, I reassembled the LED and condenser of the foldscope and made a new slide and lo and behold, when the lights were aligned  the sight was wonderful…it was a chlorophyte alga no doubt and then it struck me that the alga was photosynthesizing and hence producing oxygen bubbles.

Greedy to see more, I put the sample under an oil-immersion lens of my compound microscope (celestron — 1000x) and was satisfied that the problem was solved. Can anyone identify the species?

These algae are tiny and might have entered my flask and accumulated over time as a mono-layer photosynthesizing by the window light. I know for one that my extra-oxygenated water isnt toxic :), but the flask needs a thorough wash. The exercise reminded me of a lesson I received some two and a half decades ago from my inspiring microbiology teacher on the importance of the condenser system (I hope he is reading this).

Below movie shows a  bubble pushing the algae under a foldscope 400x.  One can also spot some Brownian motion in the alga.