Earthworms can survive for several days submerged in water in your refrigerator, which allows most of the soil in their gut to pass through their system, so that you won't dirty your tanks as much. Apparently, they find each other and don't know when to quit breeding. Probably any species of minnow that can survive in a garden pond would work just as well, but the rosies are nice because they are visible even in murky conditions. The normal fatheads are not normally visible, but at least the males change in appearance during mating, and almost act like cichlids. These fish are available from pet and bait stores in the Northeast U.S., but I have no idea where else they are available.
Green water is lower than pond scum.
The best way to make green water is to put old aquarium water from your fish tank into a clear container and place it in a sunny window for a few days. Some sources recommend putting a thumbnail-sized piece of dried lettuce to water and putting it on the windowsill, and others suggest placing a handful of grass lawn clippings in water and putting it on the windowsill. Seriously, all of the above will work eventually. Just be sure you don't dump pH adjusted water in with sensitive fish. Brine shrimp are easy to hatch, but a little harder to raise to adulthood than most hobbyists will bother with.