[Georgiadawgger]

Here's what I used to do to get really small bubbles into my HOB filter so it wouldn't make that aweful burping noise all the time...cram a 1 inch piece of chopstick into the airline...give it some time and you'll have zillions of tiny little bubbles coming out. Another option that worked for me was using UNSMOKED cigarette filter butts. The fine fiberglass is good for diffusing the bubbles too. Unwrap the paper from the butt and twist the butt into the airline. Then give the pressure some time to build and again, zillions of tiny bubbles. The only problem with both of the methods is over time (a couple weeks) you'll have that milky white buildup (like using an airstone for diffusion...you all know what I'm talking about).