I moved my betta to a 5 gallon tank yesterday (formerly in a 3 gallon) and he's pretty happy. My whisper filter is extremely quiet, but today I put my ear up to the tank and the filter makes small, but kind of loud vibrations! My betta seems to be fine and never has any problems, but I was wondering, can betta fish hear vibrations or sounds, and if they can, are they bothered by loud ones or not?
Also, what amount of temperature change can harm a betta? Like if it changes 2 degrees higher or lower, can it bring stress to the fish?