the minimum a betta needs is 2.5 gallons, HEATED!!!!!!! You could put one in the 1 1/2 gallon, just be sure to do at least 2 100% water changes a week, and don't fill it with gravel or decor, just sparsely, as that will take up space. Betta's are tropical fish, meaning they need a heater! Get ONE male or ONE female! Not two, and don't even attempt to divide anything smaller than 5 gallons. Sorry to say, but most employees don't realize the information they're giving to customers is WRONG! You could always get a nice little 5 gallon with a heater and filter, a few real or silk plants (no plastic as it tears betta's fins) and a couple ghost shrimp or a snail, and guess what? You'll only have too clean once a week (siphon/vacuum the gravel to remove waste and un-eaten food to remove about 25-50% of the water)! No goldfish either! why? they need room to grow and swim and they NEED filters as they are very dirty fish. Maybe a plant and some ghost shrimp, with mini filter BTW, will work. Sorry about my rant, it's just one of my MAJOR pet peeves when people don't research their pets before buying!