If Sea Steaders are going to create a sustainable, complete lifestyle, some thought must be given to not only engineering, of mechanical systems, of setting up a biological system alongside it that allows for growing food, and maintaining physical and mental health. there are several categories to the habitat:

1. terrestiral plants
2. terrestrial animals
3. aquaculture- marine plants
4. Marine animals
5. Avian life

•  Terrestrial plants may never achieve the biodiversity of a natural island, much less that of a continental mass, and it will be difficult to choose a robust and diverse ecology on the limited surface pace of a seastead. However, by paying close attention to the eco-systems of the closest analgos we might see more success. Plants which grow in estuary areas (appropriate to the approximate lattitudes of your particular sea stead's range), and smaller island are likely to be more successful in the environment we'll have, which will be heavily influenced by the sea. Plants which tolerate brackish and high-mineral areas are good candidates. Mangroves, and coconut palms for example might help provide stabilization for new artificial island efforts, or artificial atoll breakwaters, and also provide habitat for some of our animal species.
• Terrestrial animals will be difficult, as they typical require a lot of eco-infrstructure under them to support them, given the long sexual reproduction cycle of most larger animals, and the requirements for large ranges to support them. Probably more appropriate to artifical islands and not so much to sea steads, except perhaps as one-off purchase of larger animals to be raised for slaughtr in the same generation. It seems impractical to breed herds of anything. smaller animals might be kept for breeding cycles, but would require lots of outside resrouces both bfor the husbandry and sexual diversity of breeding stock.
• The sea stead and artifical island concept both provide a lot more opportunities for aquaculture and far more incentive than any such human endeavour in the past. Many marine plants have lots of mineral and nutritional value- the challenge will probably be to harvest in quantity in a sustainable manner, and more importantly, making it tasty. No one wants to eat compressed seaweed cakes 3 meals a day, no matter how nutritious and full of minerals they may be.
• Marine animals will undoubtedly form the bulk of the sea-steaders diet, with various fish being at the top of the list. It's quite possible to culture large beds of shellfish, fish farming is already a large-scale commercial enterprise (though many concerns about disease among fish farms and genetic diversity remain). Many cultures have harvested marine mammals for food and other products as well, and undoubtedly some sea steaders will choose to do so. Again, the sea steader will have not only a unique circumstance and opportunity to improve upon tradidional sea harvesting techniques as well as trying new technologies, but also a far greater incentive to do so, with fewer economical options that the traditional land dweller, even those who have lived upon marginal or small land masses.
• Depending on locations. migratory birds may be harvestable. Many seabirds are not considered particularly edible or useful for commercial applications, but seasteader still have that extra incentive.

In addition to the comestible and commercial value of a thriving and diverse eco-system, human beings typically just need the evidence of other life around them to be happy. A seastead made of minimal scrap might prove a technical point of feasibility and sustain life, but not a lifestyle.