Goldfish are beautiful, so maybe you’ve wondered if you can keep them in your saltwater tank. They live all around the world, so can goldfish live in saltwater?
Can Goldfish Live In Saltwater?
The simple answer? No. Goldfish can’t live in saltwater. They are freshwater fish, and their bodies are not designed to handle salinity.
Can Goldfish Survive In Brackish Water?
Some studies have shown that goldfish may be okay in brackish water. Brackish water is a mix of freshwater and saltwater.
To be considered true saltwater, water must have a salinity of 35 parts per thousand (ppt). Freshwater has a salinity of 0 ppt. So, any water with less than 35 ppt is considered brackish water.
One study suggests that goldfish may be able to survive in salinities as high as 20 ppt. But, another study says they can only survive in salinities of up to 8 ppt.
Why Can’t Goldfish Live In Saltwater?
There is a reason that most freshwater fish can’t live in saltwater and vice versa.
The reason is osmosis. Osmosis refers to water passing across a semipermeable membrane from an area of low concentration to an area of high concentration.
Put simply, water will move from an area with lots of water to an area with less water. So, if there is a lot of salt in one area, some water molecules will pass into the area to dilute the salt concentration. This equalizes the concentration of salt on both sides of the membrane.
Fish need to osmoregulate, or control the water and salt concentrations in their body. They do this through their gills, kidney, and intestines.
In the ocean, there is more salt in the water than in the fish’s body. So, saltwater fish need to keep from getting dehydrated. Yes, fish can become dehydrated, as weird as that sounds!
To prevent dehydration, saltwater fish absorb most of the water that comes into their body. In contrast, the salt is excreted out of their body through their kidney and gills. Saltwater fish also have a salt gland that continuously removes salt from the blood and excretes it from the body.
Freshwater fish excrete a lot of water to prevent becoming overhydrated. They also tend to absorb most of the salt and other ions that come into their body.
What Would Happen If You Put Goldfish In Saltwater?
So, if a freshwater goldfish was placed in a saltwater environment, they’d quickly lose water. The amount of water they excrete would speed up and they’d quickly become dehydrated.
In a highly saline environment, a goldfish would die in a matter of minutes. But, they won’t die immediately!
Many people use goldfish as feeder fish for their larger, saltwater fish. They will swim around for several minutes before they finally succumb or are eaten.
But, being placed into saltwater when your body isn’t equipped to handle it is a distressing, and likely painful, experience. If you’re not using goldfish as feeders, don’t put them in saltwater. There’s no reason to put them through that suffering.
In short, goldfish and other freshwater fish aren’t meant to handle large amounts of salt. Their bodies constantly secrete excess water. So, a saline environment will quickly dehydrate them.
It’s possible for goldfish to survive in slightly brackish water, and they likely do so in the wild. As for pet goldfish, stick with a purely freshwater environment.