Edible Algae

I keep hearing about how food is going to be in short supply at some point in the future. It hasn't hit yet -- farmers are still working hard to market all of their crops, and food companies have every interest in getting you to eat as much as possible. Still, the human population is rapidly rising, and farmland isn't infinite.
I can postpone the problem with an edible algae. A green muck that can be processed into an edible foodstuff. It'll grow in the salt water of the ocean, with maybe a bit of fertilization on our part. What we don't harvest will probably be eaten by the ocean biosphere -- winding up as the fish and seabirds that people will want to eat first. Harvesting can be done via a fleet of ships.
The oceans contain large "deserts," regions devoid of life because the nutrition to sustain them just isn't there. Maybe just feeding that is enough to make it "bloom."
But another part of algae is for my space-experiments. Algae can be grown in little tubes of water, making it much easier to keep space-bourne than land-grown equivalents. Growing an orange tree would require an elaborate hydroponics system to keep it fed and watered (and remember, water leaking in zero g is a major problem), while the algae is easily kept within its tube until harvest time. (which we can do while rotating the ship for artificial gravity, or rotating the tube for artificial gravity within the tube.)
Yes, for long trips in space, you'd need to do farming in your shuttle. There's not enough room to store many years worth of food, and you'd choke to death on your own waste within the first year if you weren't actively recycling every last bit of it. Also, farming is one of the least gross ways to recycle. (Plants smell nice, sewage refinement centers, not so much.)