That's just it, you don't want 'flying' pellets. You want a very slow tumble, just enough to keep all the pellets from moving. My problem was even on full boil, I always had issues with the pellets on the bottom going anerobic, you'll know that's the case when they turn a grayish/black color. At that point, they start producing some sort of sulpur (i forget what, sulfur dioxide I think) which can cause a crash in your tank (similar to stirring up a big DSB)