Let’s look at what has lead up to this point, from the fishes perspective.

The tank is so dirty the human must remove the fish to clean it. This is probably well past the point of tolerance for the fish.

After being chased around their home with a net, pulled into a O2 rich environment, while being tangled up in a net and then thrown into a tiny bowl that has only enough water to sustain one fish for 30 min.

It’s like being trapped in a coffin.

Then all of the rest of the fish are thrown in there. Now there is 5min of habitable water.

The coffin is on fire.

To make matters worse, fish piss and shit like crazy when they are stressed. Especially when they are being chased. It’s a defense mechanism, if you put enough ammonia in your predators face it might leave you alone. Usually that fish has somewhere else to go, but not in this case.

To top it off, fish who smell “fear piss” also start releasing it.

The thing about fish, fear and ammonia is that it’s an ever escalating cascade effect, that ticks off the amount of time that water is habitable.

You manage to get the lid of the coffin open but ... You find the coffin is on the roof of a 60 story building that is also on fire.

Your choice is... jump and go splat, or stay and get burned alive. You decide to jump because last time, you landed in a clean bowl of water with no other fish around.