I'm still experimenting with air stones and most of them make large bubbles and I don't want that. That air stone I am using is just a mod or a similar Bubble Wall https://www.amazon.com/NGe-Aquarium-Bubble-Stone-Suction/dp/B07WRJ144C (not exact one) I cut it since it's like a foam material and just tightened the other end with a zip-tie. Seems to work well.