Starting Bubbles: 60
Recommended Potions: Rainbow Bubbles, 3 extra holes in the ceiling
Clear at least a one bubble hole at the end of both rows of black bubbles(strategy picture 1). Then you have small openings to shoot at the upper bubbles to get the lower black rows to fall into the Cauldrons.
After managing to pop bubbles above the lower black rows at level 95, you need to be quite patient, trying to burst down the clusters of infected Bubbles, doom skulls and some crystals(strategy picture 2).
If you want even more guiding, please watch this videos. :)
3 Star video by the Blogging Witches (that would be the nickname for us. ;-))
Video by skillgaming