You could not fit 5-6 dwarf puffers in a ten.. You could maybe have 3!
I also nominate a betta as your best option - if you go in the betta section I did a list in there of things you need to care for a betta. They can be incredibly interactive, my ex has hers trained to know when she taps the food twice on the desk by the tank, it's feeding time. The fish swims from wherever he is in the tank to the top where he is fed every day! Shrimp might work, or they might be a pricey snacks best to check out your bettas temperament first. Pygmy corys are a great option. Ottocinclus catfish (6+ as they are schoolers) are another one. They are algae eaters.
I also nominate a betta as your best option - if you go in the betta section I did a list in there of things you need to care for a betta. They can be incredibly interactive, my ex has hers trained to know when she taps the food twice on the desk by the tank, it's feeding time. The fish swims from wherever he is in the tank to the top where he is fed every day! Shrimp might work, or they might be a pricey snacks best to check out your bettas temperament first. Pygmy corys are a great option. Ottocinclus catfish (6+ as they are schoolers) are another one. They are algae eaters.