Why do BTAs stop bubbling?

[Myka]

There is no real 100% accurate explanation for this. I've had on more than one occasion, a bubbly BTA split and have the clone not be bubbly or vice versa - in the same tank, side by side. I've had BTAs from different collection locations as well as propagated BTAs under all sorts of water conditions and lighting, as well as well fed and half starving, and there is no rhyme nor reason nor any pattern than I can discern other than possibly that bigger BTAs may be a bit more likely to not be bubbly. That is a rather "loose" observation though.