Betta Bowl Care [Help]

Hi everyone! So, I recently got my first betta fish in over a decade. His bowl seems to develop a film of sorts over the top of the water, despite me changing the water about once a week. I have my fish, Levvy, in the bowl, along with two small snails. Is this normal, and should I just stay on top of changing the water? I use Betta Basic water treatment, as well.

Thank you!