Algae, Liverworts, Hornworts
Ask your local aquarium dealer about the plants that are stocked in this whomever's aquarium. Not all algae is edible, and in truth, I have only done this as per specific recommendation using a specific type of algae. Aquatic mosses are less dangerous, however, I have not tried these, and am going to spend several months reading up on bryophytes prior to even thinking about it. Read up on bryophytes mosses, liverworts, and hornworts prior to trying this.
Go to your oriental food store and pick up some dried seaweed or Nori. See if anyone there knows about their product. There are also varieties of Celtic seaweed, Lavosh, or Lavash that might be in stock; though it might be a Middle Eastern flatbread.
I would not recommend this for anyone who does not have an immaculate aquarium, with respectful housemates. Pure water is an absolute must for having excellent tasting greens, as well as high-grade water filters that are changed regularly.
A ten to twenty gallon tank should be enough, as there is less to clean up when equipment wears out or an accident happens.
Moreover, the tanks can also be used to keep feeder goldfish in stock while a prospective algae grower is testing the house. My housemates really, really liked the feeder goldfish.
