Here are some notes:

I tend several client tanks every week.
One is a larger tank, with high light, 28" deep.

The upper part has Java fern. Lower parts, other species that are much faster growing, thus more likely to pearl.

After the water change, there is no pearling in the first few minutes.
Then, without fail, the places with the highest light intensity begin to pearl first(10-20 minutes after the water change).

This pattern is consistent.
The faster growing Rotala does not pearl and is not close to the higher lighting.

Thus one might think this suggest that the Photosynthesis, driven by higher light=> pearling, rather than excess air accumulation, or sticky degassing bubbles.

My experineces with degassing bubbles contends that they appear almost immediately after the water change, and they stick to everything/everywhere in the tank regardless of lighting......that is if you accept that they are degassing bubbles, which clearly in the Java fern/Rotala case, I do not see how they possibly could be.

This observation and rational suggest that it is not degassing, it is light driven photosynthesis.

Degassing bubbles should stick to everything regardless of location and orientation.

But this is not observed in this tank or my other tanks.
Also, one can do daily water changes and see this same effect repeated every day and a higher growth rate.

The other way is to run an O2 meter and measure the Oxygen, which is higher on water change days but you could argue that the bacteria drain more as the organic matter accumulates through the water etc(adding AC or Purigen etc could act as a control and remove that fraction though).

So it's not just what is in the water, it's also exposure to the air itself.
If it was merely excess gas taken into the plants, you also would not see localized pearling relatable to the lighting.

It offers up more proof towards my contentions about water changes and adding CO2 via gas phases.
I know it's not sticky air bubbles and degassing water in the above cases.
I know what I am seeing along a lighting gradinet is photosynthesis.

I saw that pearling along the lighting gradient(light and pearling are proportional) and knew right away what it meant.
It answers the question in these tanks about water changes, exposure to air etc.

I can also drain and fill at the same time and thus change almost all the tank water with no exposure to air also........so that would give me a tank with a large water change and no decline in the water level, and see if the same patterns exist.

That's next.


Regards,
Tom Barr