What is this thin-stemmed plant with narrow leaves in an aquaponics bed in my greenhouse?

Question

This plant grew from seed to about 2' high within 3 months. I'm sure it's not done growing. I have no clue what it could be, since I'm in the bad habit of sticking anything that looks like a seed into the soil. It could come from the grocery store fruit or veggie, it could be a seed that I did not label etc. It's inside a greenhouse, growing in an aquaponics bed. I hope it is edible :-)

Answer 1

Also looks a bit like a mustard or rocket plant.