Simple Guidelines to Soft Water vs Hard Water for Aquariums

If you’ve been searching for information about aquarium keeping, you’ve probably seen mentions of water in terms of hardness and softness. Here’s a super easy-to-follow rundown of the differences between hard water and soft water and why it even matters.

The Difference Between Hard Water and Soft Water

Basically, hard water is rich with minerals (like calcium, magnesium, and iron) while soft water is very low on minerals, sometimes to the point of having almost none.

How does this affect the water? Well, for one thing, minerals in hard water interfere with the formation of soap suds; soap lathers more easily in soft water. Ever boil water in a pot and noticed a white powdery coating inside the pot afterward? That’s limescale from calcium in the hard water – boiling water can sometimes make it softer when it cools, depending on which minerals were in it.

Tropical fish, as well as tropical aquatic plants, generally prefer soft water. Inconveniently, the water coming out of your tap is probably quite hard.

How do you know if your water is hard?

It’s a breeze these days! Water testing kits are widely available. Carbonate Total Hardness Test Kit for Freshwater/Saltwater or the GH KH Hardness Test Kit for Freshwater will do the trick just fine.

How do you soften water?

So, your test kit is saying that your water is too hard for your tropical fish. That’s okay, because you can soften it! There are different ways to soften water. First, you can try adding water that has been treated by reverse osmosis. Most grocery stores carry reverse osmosis water in the bottled water section. Secondly, you can add a water softener product (like Rena Filstar Water Softener Pillow) to your aquarium’s filter. Finally, there are water softeners that will filter water for the whole house (like Pelican PSE1800 Whole House Water Filter and Softener) but this last option is quite expensive.

There you have it, the ABC’s of hard water vs soft water and how it relates to your aquarium of tropical fish!