Floating FISH! (Alliteration!)

I feel like I have a lot of either one word titles or all-caps titles... but that's ok. :)

So when I was doing my physics homework, I saw the section about how fish use their swim bladders to go up and down. Immediately, my two fish (one goldfish, and one betta) came to mind.

Both fish expand or compress their swim bladders to deeper or shallower in the water. They fill these bladders with gas that their bodies produce, and when they expand their bladder, their density decreases while their volume increases. This makes them go up in the water, since when their volume is greater they displace a greater volume of water which causes a greater upward force. Likewise when they want to go down, they compress their bladders, so that their density increases as their volume decreases. This makes less of a displacement in the water, so the upward force (F = pvg) is less.

Occasionally, fish will get swim bladder infections or be born with a "broken" swim bladder. This means that they can't easily go up and down in the tank, and will often float sideways or upside down. Sometimes they won't be able to move in the tank much. :( And then the fish die. (My poor deceased other goldfish, who died a few weeks ago... )

This is a video of my goldfish swimming around in his tank! (The betta decided to hide from the camera.)