We can use a tube attached to the bottom of a plastic bottle aquarium for different purposes (check the previous video).
We can use it to remove fish poop.
We can use it to add water to maintain the level.
We can attach an air pump to the same tube.
Turn the air flow regulator on low or off.
Attach an air pump to the tube.
Turn on the air pump.
Adjust the air flow to a desirable level.
The air bubbles increase water surface, contributing to better oxygen levels, in the water. The bottom to top water flow improves water conditions on all levels of the aquarium. The water flow is beneficial to fish in the same way a treadmill is for people :)
Have fun and happy aquarium :)