hey fellow college student! 3 days new? NP :D you cna still return that tiny container!
you can definitely divide a larger tank. 2.5gallon is the minimum size for a divided tank (going with the atleast 1 gallon/ betta rule)
5 gallon is even better
and 10 gallons will be great!
as people have stated above. you do need a heater (this is one of the cheapest and best)
you should also get your fishies some silk plants :) ones that wont hurt their fins!
eventually I recommend you to look into getting a filter so the tank can cycle :)
(to make the tank safer for the fish! and may be less water changes when ur busy with your studies!)
I highly recommend this one
you will definitely need a 50% waterchange half wy through the week and a 100% watee change at the end of the week for a 2.5gallon :)
and if u are in the states, you can get a 6 month free 2 day shipping plan if you are a student! woot!
flakes are not terrible, but being so thin, the nutrients leches uickly into the water and doesnt leave much for the hungry fish!
pellets retains the nutrients muh better and will be a healthier alternative