What do the bubbles in this video come from?

[Mordachai]

Freshwater Planted Aquarium - Cloud Mountain |

I've seen other videos like it from professional aquascapers. But I don't yet get why their substrates seem to be bubbling, unless their plants are that productive???

 

[Billbug68]

It's the plants producing oxygen.

 

[Fishperson]

It's the plants producing oxygen.

Known as pearling.

 

[dragonfisher33]

and it's because the water is saturated due to the plants photosynthesizing. this is the epitame of highly aquascaped planted tank with rich substrate, light, and carbon dioxide

 

[Mordachai]

Wow. That's gnarly. Something to shoot for