Turnip greens, romaine lettuce, spinach, softened in the freezer, are "appropriate for marine life". I've heard countless times that marine fish should only be fed marine-based foods. However; spirulina algae, certainly the most common SW herbivore food and PE Mysis, possibly the best frozen SW carnivore food---are both FW products. With nori available, I don't feed many garden veggies, but there is certainly nothing wrong with them. IMO & IME. I've seen well -known Public Aquariums (like Aquarium of the Americas, prior to Katrina) , feed romaine and spinach by the case.