Found out how to do this on YouTube. Mine is basically the same as that guy's but I used a small zip tied instead of a pebble to put at the end. This way, the end is straight and the bubbles come out straight, and it blocks the end. Just put the small zip-tie in the end of the tube and it fits in there perfectly. Then I just added hot glue on the end just to make sure it's secure. Then I used a small scissors to poke small holes in it like he did, be careful here! Haven't tested it out yet, but here is the finished product.