Aquaponics is a great way to make use of limited space to grow a variety of food, including raising fresh fish. The beauty of it is that any vegetable where the edible portion grows above ground can be grown this way, with the root systems underneath in the tanks that are then used to raise a variety of edible fish, the most popular being tilapia, but you can use other varieties, though those that grow quickly are probably your best choices. The plants help filter the tank, and the waste and water from the tank helps nourish the plants above. This means that in one closed system you can raise a variety of fresh vegetables and fish to give you more variety in food choices for living off the grid. It can also just be a fun family project that can help teach children how the cycle of life works, and teach them a valuable skill for use in the future.
You aren’t limited to just fish, as you can raise any aquatic animal in your system, including snails, prawns, and crayfish, so there is a lot of room to use your imagination if you have enough resources to make sure you have the proper system setup for a more diverse system of life in your tanks. Keep in mind though, the more complex your system is, the more care it will require, though it will still be less than trying to raise both separately. Also, some plants do better after your system is more established and you have a higher density of fish and other aquatic life as they will require more nutrients from the waste in the water below. There is a wide variety of information available online, from small starter kits made more for small fish and some herbs to much larger systems with a more complex system of plant and aquatic life.
For more information you can start here https://www.nal.usda.gov/afsic/aquaponics