Kyle E.
Fish Crazy
I saw a video (I tried to find it but couldn't) where the person put a 5 gallon bucket of water outside in direct sun and it grew a bunch of algae. She then put some brine shrimp in and just left them, and they fed off of the algae. I presume you would need to heat the water or something for that. It seemed like the easiest way I have seen.
