I know there are some in my cichlid tank, but I never ever see them, they're usually just a couple in my HOB filter, but that's about it. I have a colony in my planted tank, but I only notice them when I happen to be overfeeding or if I stare at the sand bed really closely and see tiny grains moving. I use pool filter sand in both of the tanks i mentioned and have never had a problem with anaerobic air pockets. And whenever I see one, I just give it a slight brush, and it usually releases it, but yea, just make sure you're giving a few stirs for the first week or so because that's when air pockets usually are formed, after that when the sand has been fully soaked, from my experience, air pockets almost never form again.