When a saltwater fish is placed in a freshwater tank, it will unfortunately die. This happens because the significant difference in salinity between the fish's body and the surrounding water causes a severe physiological imbalance.
The Science Behind Why Saltwater Fish Cannot Survive in Freshwater
Saltwater fish have internal bodily fluids that are less salty than the ocean water they inhabit. They constantly drink saltwater and excrete excess salt through their gills and kidneys to maintain the correct balance (osmoregulation).
However, placing a saltwater fish in freshwater reverses this process dramatically.
Based on the provided reference:
- Freshwater is a hypotonic solution compared to the fish's internal environment. This means the concentration of solutes (like salts) is much lower in the water than inside the fish's cells.
- Water molecules naturally move from an area of high water concentration (the freshwater) to an area of low water concentration (inside the fish's cells) through a process called osmosis.
- As the reference states, "the fish will take too much water in its cells".
- This excessive water intake causes the cells to swell.
- Eventually, the cells will rapture (burst).
- The accumulation of water and bursting of cells throughout the fish's body ultimately causes the fish to die.
In essence, a saltwater fish in freshwater is overwhelmed by water influx it cannot cope with, leading to fatal swelling and cellular damage. Their bodies are simply not equipped to handle this drastic change in environment.
