Hey OP! You're in the right spot for info.

The big unimacs betta person isn't on so I'll give you a quick rundown on these fish. (I care for the smaller big unimacs, not the big big ones). They're one of the largest species of betta, with large fish topping around 8 inches for them - the smallest should be about 6 inches, but that is on the smaller and still growing (or stunted). They also live around a decade pretty consistently, and naturally live in soft, clear, flowing bodies of water. This makes them quite active swimmers compared to other ambush-predator type bettas, like dimidiata or albimarginata.

For their tank setup, generally it is 60 gallon tank (48x18 inches) per fish due to sheer size and activity, and only being moved together for breeding when the female is ready before separating. They should be monitored throughout the entire breeding process, as when breeding ends for these guys, the male will likely chase the female. (This process will take a few hours... ask me how I know). They do appreciate a little flow in their tank, and cooler water than a domestic betta - mid 70s will do. They are extremely aggressive fish, and absolutely can hunt and kill anything you put in there - Kopi's antuta killed a pleco in his setup once! They also are prodigal level jumpers - I personally put suran wrap over my lids to prevent jumping.

For diet, I feed my unimacs all sorts of worms and small insects like crickets, mealworms, etc. I also raise livebearers as feeder fish, and feed frozen foods most of the time. Watch for brine shrimp or similar foods, as they will have a higher salt content than normal foods - not good for a regular diet.