Have you notice that your aro frequently like to yawn? Whenever he feels like. He will yawn.
In human being naturally we do yawn when we feel sleepy. In science and medication they do research when somebody at your side yawning, the next person will yawn too. They speaks that we inhale oxygen whereas in the blood cell need more oxygen into cell system. That means lack oxygen in the body and inhale oxygen after that we purged (exhale) carbon dioxide more in the process. So that effects too to the next person, he will takes the carbon dioxide when other person yawning, effect to him too to be yawn because he inhale the carbon dioxide. He will be yawning too again to new fresh oxygen. Logically thats explained.
What about yawning with arowana? Full oxygen consist above the water level (atmosphere). Inside water will be less, unless we do the water flows. Molecule will breaks and the oxygen will enters.
Therefore enough about chemistry, its said to be in arowana the blood cell needs oxygen too. If the water aren't enough flowing they like to have a small gulp frequently to catch up oxygen. If the water condition is good, and the arowana is comfort. They just yawning to inhale the oxygen whenever they like. Yawning act is their natural habit / act. They like to yawn when they feels comfort.
If your water polluted or contain high chlorines, they will start to gasping on water surface. Need to inhale fresh oxygen from surface. The contaminated water (high chlorine) will kill the fish. It will be corrosive for them hence killing their internel blood system.
Some people said, the arowanas like to yawn because to exercise their mouth and jaw. Like other animals too, the cats like to scratch on sofaor any hard materials to sharpen their claws. Some goats or deers like to bang their heads each other to sharpen their horns . I believe every each animals in the world have their own habits.
When I do my water change, I wait untill my arowana starts to yawn. After that I feel better when they yawning. I confidently leave my tank and do housekeeping to clear my hoses. Are you making the same too?
Thanks for reading!
Note : Please be sure whatever you do. The information above is just for knowledge. Water change do for extra precaution and monitoring. Not for amateur application . Trust your testing kit.