Back near the beginning of May, I found green algae growing on the roots of an avocado seedling I had growing in a jar of water on a sunny windowsill. I've been culturing this algae in 1 liter soda bottles roughly three-quarters full of 0.5 µm filtered tap water and a pinch of Miracle-Gro plant food powder (Miracle-Gro product # 1001123). A pinch measures somewhere between 0.1 and 0.25 grams on the most sensitive scale I own. As a best-effort yet quick and dirty attempt at sterilization, I heat the Miracle-Gro solution in the microwave with the 1 liter bottle closed for 30 seconds at a time until the bottle feels uncomfortably hot to the touch, which I believe is in the 140°-160°F range. I wait for the solution to cool to room temperature before inoculating with ~2 mL of a previous culture that is obviously green to the naked eye. I put the open inoculated bottle on a sunny windowsill here in Boston and let it grow for a few days. The contents turn noticeably green within 4 days in the Boston summer sun.