Hi, I have two fish and one of them has grown to be significantly larger than the other. Today I changed their water and ever since then my large fish has been acting crazy, he’s swimming back and forth really fast in a consistent pattern and shaking his head back and forth and is snapping at the top of the water, while my other fish is chilling out, perfectly fine.

最佳回答：

I would recommend to add more water conditioner and if it is still happening, then to have the water tested at your local aquarium store. There could be something off in the PH or ammonia levels. You did not mention if this tank contained a bubbler. It could also be decreased Oxygen in the water and a bubbler will fix that. Please post again if you have any further questions!