i have an airstone that's a few inches long... i guess you'd call it a bubble wall. but since i've had it, bubbles seem to only be coming out of the half closest to the tubing. is there anything i can do to make more bubbles come out, or do i need to buy a new one?

That means ur pump is not strong enough to push the air the whole length of the airstone. Get a stronger pump or a smaller airstone

okay, that makes sense. thanks!