How to Start Growing Spirulina at Home | Beginner's Guide to Grow Blue-Green Algae | Start Your Tank 

"Avoid distilled water or water treated with reverse osmosis as they lack essential nutrients" gee, it's almost like the very next thing you're going to do is add all the essential nutrients to the water! Distilled or otherwise very pure water is the perfect blank slate for creating a solution where you have exactly the right amount of everything, all perfectly balanced for your spirulina culture. You know there's nothing there, so you just add everything you need in the amounts you need and you're good to go. Most authorities recommend pH 10. The more alkaline the solution, the harder it is for anything else to live in it, which makes it easier to maintain a pure culture of edible spirulina, so long as you don't go so high that even spirulina can't handle it. There are many other things that live in warm water with plenty of nutrients, and some of them are extremely toxic, so if your culture starts growing anything that isn't spirulina you have to throw it away and start again. Spirulina does not need "proper oxygen circulation." Oxygen is a waste product of photosynthesis. The spirulina will re-uptake a small amount of oxygen in respiration during its sleep times, but it will get this out of the water around it without any help. It needs good aeration because it needs carbon dioxide from the air, and the agitation caused by good aeration will help *remove* excess oxygen from the culture. 3:39 the way those blurry green dots are rushing all over the place .. unless you're agitating the water a lot, those aren't spirulina. Spirulina doesn't move around of its own accord - the most it can do is adjust its buoyancy to make itself float or sink. Those look more like some sort of zooplankton that have turned green from having a belly full of your spirulina while being so small their own bodies are transparent. If there's anything on a standard microscope slide that is moving too fast for you to focus on, your spirulina culture is contaminated - throw it on the compost and start again. I'm pretty sure I've seen most of this footage already this week. Maybe don't steal footage?