What best explains why freshwater aquarium would be a dangerous habitat for saltwater fish?

Freshwater aquariums are dangerous habitats for saltwater fish because of the difference in salinity levels. Saltwater fish are adapted to live in water with a high salt content, while freshwater fish are adapted to live in water with a low salt content. If a saltwater fish is placed in a freshwater aquarium, the water will be too low in salt for the fish to survive. This can cause the fish to become dehydrated and eventually die. Additionally, the freshwater aquarium may contain harmful bacteria that the saltwater fish is not adapted to, which can also lead to illness or death.