the thing is for this project its meant to be self sustainable, and have a happy populace. the easy part is self sustainment on a lowtech scale, but to have people happy means having all the possible sources of food. if some family that enjoys the taste of beef moves here, the adjustment will be very large and cause a cascade effect as they are unhappy with the fact that every meal with protein is fish and tastes as such, other problems include allergies to seafood. by giving the population every possible source of food I can in specially maintained microclimate biodomes, not only do they get to leave the crowded city for the local vacation spot which helps to sustain their nutritional happiness, but they get to feel like they went to a far off locale for a vacation, despite being able to do so every weekend.
by providing every possible livestock I can, it also gives the entire city it's own economic power in the greater world, by being in the seas, we can ship our products around the world for a slightly lower cost because we are effectively more centrally located as compared to the other nations to each other. this in turn allows us to draw upon the people of any culture to create a greater more diverse melting pot of culture and learning than has ever been seen in the world, a place designed to make every one of every skin color and culture feel at home by what they can cook if not what it looks like, and a city with so many languages that eventually everyone knows just about every language and there aren't as many cultural barriers between people anymore. granted I know the city will automatically subdivide into ethnic groups, but if my plans are allowed to go to fruition, people will be given homes based on their localized needs, and not their ethnic background. maybe one building will be a condominium with all one ethnic background to make them feel more comfortable around their neighbors, but the city block will have about as many as the rest of the city.
but some people will be vegan and so we have the various vegetable farms, and until I can find a way to hire someone to be in the position to monitor the various farms that is their expertise, I have to make sure I can do it. for all I know I will be trying to pull this off singlehandedly, so I have to sprout extra fingers, just so I can keep one in every part of the pudding until I get someone to handle it better. some people will be vegan, so we have farms, some people are going to be down home redblooded carnivores, if that's the terminology you want to use, and would rather leave with their family, than go without a good juicy steak every week. my problem is, while I'm not picky, I do require certain skills and skill sets, but the people with those skill sets might be the picky ones, and if that is the case then I have to meet those needs to fill those jobs with the most qualified people I possibly can.
and there is nothing wrong with a 100% self sustainable city. I chose the ocean because it has a decent location, it has problems if their comes a tsunami, but I plan for the entire city to be submersible on a very carefully monitored and controlled vacuum based ballast system, meaning the entire thing can go atlantis and sink beneath the waves in the event of a bad storm, sadly this will be disorienting, but eventually citizens will hopefully get used to it. it will prevent waves from capsizing the city in a hurricane, or buildings being damaged, by simply not being effected whatsoever by the waves. there will be areas for fish farming, but the external ecosystem is not meant to be interacted with in any way, the city is meant to be in a portion of the sea with few if any currents, utilizing a buoyancy based ocean hydroelectric generator, but that is the only external extent of the city. it wouldn't be too much different on another planet, sure you have to worry about making enough atmosphere to block harmful radiation, but you might be able to make an external device for that purpose, but otherwise the power system is meant to be externally generated, on things like solar panels and such.
I wish it were so simple, but sadly the scope of the idea is too large to be able to succeed based on cutting the food supply down in such a way. however if I can get the idea off the ground as even an oceanic research base we can study the various effects of the denizens of the ocean which surrounds us to better our knowledge of the ocean, the creatures there in, and maybe make some breakthroughs that could be useful in other fields of science. perhaps we could find a type of algae that produces more oxygen, this would be highly beneficial to grow as a crop of some variety to help in case of extended storms or for use in a space program.
as I named the post, curiosity can go a LONG way.