Well i was curious, so why not?

bucket & rain water.
got the fishtank airpump, hoses & bubblers from a pet store for under $40

you can use tapwater too, it'll take a day or so in the sun for the chlorine to disappear.

I didn't have any algae to start off with, this stuff just grew in there on it's own. In a few months this is what my new pet looks like.

No fertiliser (cept the bees that drown themselves). I'm considering peeing into it.
no CO2.
just air bubbling through and direct sunlight.

couldn't be cheaper.

If you're wondering what the other thing is becide the white bucket, it's another bucket i've lined with cheap reflective Mylar (ie: an emergency blanket). The shiny aluminium layer is eroding off in the water though - should have faced it backwards.

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I'm planning on grabbing some clear "polytube" packaging plastic and using that instead of the bucket. Like these guys: http://tribes.tribe.net/chlorophyllcollective/photos

Also i'll add a bit of pee into it, nitrates! Should make it go mental.

I wonder if algae could be used instead of tree plantations - for CO2 offsets. Afterall algae is the fastest growing (and fastest CO2 absorbing) plant, why bother planting trees?

It grows at an insane speed if you directly feed it CO2 emissions (and some are doing this, see my other videos), but even if you just feed it normal air it grows way faster than trees. (less info)