All across America and the world, people will most likely find that fish are an easy animal to keep and maintain for long periods of time. That being said, everyone who seeks to own fish have different preferences compared to other people, whether that is in fish, the type of aquarium or bowl they choose to own and keep their fish in, or even where they buy their fish in the first place. This then begs the question—is the aquatic life in your aquarium safe if you use a water softener in your home? The answer is both yes and no.
The Equipment & Type of Fish Matter
Sometimes, water softeners can work in specific aquariums for specific fish. It will depend on the company that sells the aquarium along with the type of water softener you buy. Ultimately, if you want to set up an aquarium in a home that uses a water softener, you will need to look at information from the manufacturer of the water softener or do research into the specific type of fish you own or want to buy.
Not all fish have the same needs. The compatibility of a water softener and an aquarium will also depend on the specific needs of certain fish. An easy example of this would be that a goldfish has different needs from a betta fish, including even the type of food they eat. Sometimes, lifespans of fish will differ as well, and that could also depend on the way aquariums are set up.
It also depends on if the fish you own are freshwater or saltwater fish. In this case, water softeners might be better for the freshwater fish but harmful for saltwater fish. As for the second option, the closer that you can keep your water in the aquarium to sea or salt water the better.
Worries & Cautions
The thing about water softeners is that they tend to decrease the amount of chemicals in the water, some of which are needed for fish to survive. The way that most water softeners work is that they replace the calcium content in the water with sodium content. Certain fish do not do well with high sodium content in the water, and in those cases water softeners would not be a good option to use.
For other fish, it might not be a problem with the high sodium but rather the lack of calcium or magnesium that might cause them not to live long in an aquarium that a water softener has been used in. Also, a lot of fish need minerals that form limescale, whereas water softeners are designed to remove said limescale-forming minerals. In this case, it would be better to use water treated by a softener for washing machines or dishwashers and less so in aquariums.
Altogether, the usage of water softeners is up to you, along with the specific needs of the fish you wish to have living in your aquarium. Most likely, a lot of research into your water softener and its manufacturer along with the specific fish breed will be needed before you decide whether or not to use the water softener that you have.