Any way to reduce the air flow from a too-big air pump?

I've got a new air pump working with a sponge filter in my betta tank, and the pump is adjustable, but even turned all the way down, it's still putting out enough bubbles to produce more current than I think my betta would be used to in the wild. It's this way with both the air stone and without the air stone. Is there any way to tone that air flow down without harming the pump? Thanks.