Very unlikely. Ammonia poisoning can kill fishes in a closed small aquarium, but this fishes are coastal and marine and very mobile. In the ocean we would need

Very unlikely. Ammonia poisoning can kill fishes in a closed small aquarium, but this fishes are coastal and marine and very mobile. In the ocean we would need an awful lot of ammonia for the same symptoms. And we would have a very noticeable bloom first in the water joined with tons of stranded dead fishes.