I never knew this

[MattW]

at 29:00 minutes talking about how bubbles can show amounts of ammonia and nitrates etc

 

[Ichthys]

With mature filtration you don’t get any build up of ammonia. Bubbles not popping is about films on the surface. Any protein or fat presence in the water (mostly from foods) will form a film on the surface and prevent bubbles from popping quickly. It shows you need to skim the surface (to aid gaseous exchange) and probably change the food, in my experience.

 

[Ram419]

I suppose if you mess up and feed too much or there's death in the tank causing ammonia spikes that would be true. There's plenty other reasons to see bubbles, as Ichthys mentioned probably the most common one. Here's a good list of all the reasons for bubbles in the aquaruim --> https://www.aquariumcoop.com/blogs/aquarium/bubbles-in-fish-tank-water