Where can I farm Aqua Pearls?
Following that same link you provided, it also suggests enemies that drop the item in the campaign.
Doing some more research, some suggestions have stated the "best" place to farm is the Ballen Passage Entrance stage (found in Dirnado).
The levels that contain monsters that drop these items are:
- Downhill
- Narrow Path
- Crossroads
These missions also only require 4 energy each, as opposed to the 5 - 15 that the Chamber of Awakening trials require.