I have to admit something, I squirt a lot of shampoo into my friends populated aquarium.
Why would you do something like that? Is your friend and the fish okay?
She was fine, but the fish weren't fine.
That doesn't mean it's okay to go on a rampage and destroy her things and her pets. Those poor fish didn't ask to be poisoned, and you ruined a whole ecosystem in the aquarium. You need to pay her back and apologize.
I don't plan on it.
You haven't given any justification to what you did, and there really wouldn't be in a justification. You need to apologize for it to your friend for what you did. There's no sense in hurting harmless animals.