The survival of our pet fish partially depends on the number of minerals present in their environment.
In this sense, the chemical composition of spring water makes it seem like one of the best sources of water for a fish tank.
This is unsurprising since it also lacks any artificial disinfectants that may harm fish.
But is spring water actually safe enough for our pets?
Can you use natural spring water for your fish tank?
Natural spring water can be a hit or miss if you’ve set your mind on using it for your aquarium.
Whether this type of water is good or bad for your pet fish has to do with its origins:
Spring water is defined as any water that comes from an underground source.
Along the way to the top, this groundwater dissolves different minerals from the surrounding rocks in itself, most prominently Magnesium and Calcium.
This makes it mineral-rich which means that it essentially turns out hard when it reaches the surface.
At this point, the question really becomes whether hard water can be used in a fish tank. There are plenty of aquarium pet fish that thrive in hard water, and for some of them it’s actually a crucial part of their natural environment.
Some freshwater fish that do well in hard water aquariums are:
- Livebearers such as guppies, the platy, swordtail fish, and Mollies
- Some species of killifish like the Golden Wonder killifish
- Some species of rainbowfish
- African cichlids and some species of South American Cichlids
- Some Barb species
Sounds promising right?
Before you draw conclusions consider the following:
The metric used to show how hard water is is called General Hardness (GH).
GH measures just the total sum of all minerals dissolved in the water.
However, no one really tells you WHAT those minerals are.
And this teeny-tiny detail becomes relevant if you’re to put live fish in that water.
For any naturally hard water, the largest portion of minerals responsible for its hardness is Magnesium and Calcium. And contents of both minerals, as well as GH, can vary greatly across springs the water was collected from.
Fish, unlike land animals, draw the majority of minerals needed for their bodily functions from the water they live in and not their food. Research suggests that a skewed Calcium to Magnesium ratio of water can affect how freshwater fish that live in it develop.
My research on this shows that the ideal Ca:Mg ratio for freshwater aquariums should be between 3:1 and 4:1.
However, this is more of a reference point than anything and is not something you should obsess over.
Issues may arise only when the Ca:Mg ratio in your particular spring water is hugely skewed (something like 20:1).
So from this, we can conclude the following about using spring water in a fish tank:
You should test how hard your spring water is and then research what water hardness the fish in your aquarium prefer living in. If the two align nicely, then you can use the water in the tank. Ideally, the water should contain a balanced Calcium to Magnesium ratio of between 3:1 and 4:1.
Getting a GH test kit is the simplest way to determine the hardness of your water source. There are also water test kits specifically designed to detect Magnesium and Calcium.
Is Bottled Spring Water Safe for Your Pet Fish?
Conveniently having a natural source of spring water nearby is not something everyone can boast about.
Store-bought bottled water goes through treatments that may affect its usability in fish tanks:
There’s a slight chance that bottled spring water is disinfected with chlorine.
To be on the safe side, use a water conditioner to dechlorinate the water before using it in your aquarium.
Most manufacturers of bottled water typically use ozonation or chlorination to disinfect their product from potentially harmful bacteria.
In the cases where the water is treated with chlorine, there’s typically a follow-up procedure to remove any leftovers of the chemical.
However, this practice is not really guaranteed, and we as fish keepers should be what I call “pessimistically careful” about what we put in our precious aquariums.
A very popular water conditioner used to dechlorinate water for aquariums at home is Seachem Prime. Prime is basically a bottle with solution you treat water with before putting it in your fish tank.
Closely follow the instructions and your pet fish should be safe. There are also more natural ways to dechlorinate water at home but most of them are somewhat impractical for fish keeping because they take too much time.
How does spring water compare to other aquarium water sources?
- Tap Water
As many would confirm, tap water is a decent water source that you can use to start an aquarium.
Unlike spring water, however, you can be certain that water from your sink contains either chlorine or chloramine. If your only alternative is to use tap water for your fish tank, make sure to treat it with a water conditioner beforehand.
When comparing tap and spring water to each other, I believe that spring water is a better option for someone looking to fill their tank.
Drinking water in older city systems also has too many artificially added phosphates to it, which can induce algae issues in an aquarium.
On top of that, water quality varies from region to region. It could be that your tap water turns out perfect for your fish but your neighbor’s tap brings a disaster for theirs. Learn more on tap water and its effect on your tank.
- Distilled Water
Distilled water is not a good option for setting up a fish tank, which makes spring water the superior choice.
Distilled water goes through a pretty rigorous filtration process that eliminates bacteria and metals, but it also removes helpful minerals such as calcium, and magnesium.
Spring water may be cleaned with chlorine for killing harmful organisms, but it still retains a lot of helpful minerals after the process.
So, if you had to choose between spring water and distilled water, I would highly recommend spring water as the better option.
This doesn’t mean that you can’t ever use distilled water in your aquarium journey, but it shouldn’t be the first choice.
Due to how thoroughly the water is purified, you would have to add a lot of minerals that were stripped during the purification.
If your tank water has evaporated somewhat, distilled water is a good option to top off the losses.
That’s because evaporation does not mess with the mineral contents in the aquarium. To learn more about distilled water and why it isn’t the best choice for your fish, click here.
- Reverse Osmosis (RO) water
Reverse osmosis water is purified by filtering any type of water through what’s known as a semipermeable membrane. Chemicals, metals, and other contaminants get filtered by the membrane.
In terms of quality, RO water is similar to distilled water.
This makes spring water better as it is an almost ready-made solution for an aquarium, unlike RO water.
- Deionized (DI) water
The main difference between spring water and deionized water is mineral/nutrient retention.
None of the minerals that naturally come with spring water are removed in its disinfection.
On the other hand, Deionization strips the water of its mineral content and even removes Nitrate.
Additionally, Deionized water does not filter bacteria. Some bacteria will be helpful to the ecosystem of your aquarium, but others can prove to be quite the problem if left to dwell with your fish.
All in all, spring water is a way safer bet for aquariums than Deionized water.
- Purified water
When comparing spring water and purified drinking water to one another, spring water comes out on top, here’s why:
Purified water lives up to its name of being pure, meaning that it lacks a lot of vital minerals and nutrients needed to sustain your aquarium fish.
Although spring water may contain chlorine which is toxic to fish, the chemical can easily be removed by a dedicated water conditioner.
Purified water is basically any water that has gone through some form of purification.
The purification process could be distillation, reverse osmosis, or deionization.
Adding purified water to your aquarium without any intervention will ultimately kill your fish due to its lack of essential nutrients and minerals they need.
If you plan on using purified water to fill your aquarium, make sure to take the needed steps by putting back in minerals and salt to balance them to appropriate levels.
Author’s note: Water purified with a sand filter cannot remove harmful chemicals, so keep this in mind when picking what brand you want to use.
- Mineral water
After researching mineral water versus spring water, I discovered that they are fairly equal in terms of their use in fish tanks with the favor leaning towards spring water.
They also both contain vital minerals and nutrients that fish need to survive.
Mineral water, same as spring water, is ideal for aquariums with fish that need higher GH. Mineral water, like most bottled water, is treated to be fit for human consumption, which typically means it may contain some chlorine.
Mineral water may be collected from under the ground, similar to well water.
However, some companies just purify water and then artificially remineralize it.
What type of water would be best for aquarium fish?
When looking at all the options available spring and mineral water shine as the best ones to use in an aquarium with fish.
Tap water is also feasible and commonly used as it is the most accessible option.
You will have to treat all of them with a fish water conditioner of some sort, but you won’t have to worry about essential minerals being stripped away.
This is all based on the premise that you would keep fish that do well in hard water.
Keeping soft-water fish is not recommended for beginners. This is because these species are more sensitive and it’s an overall difficult task to keep soft water stable.
Author’s note: One of the most common fish sold to beginner aquarists is the Betta fish (Betta Splendens). These fish are commercially bred in hard water conditions to make them more adapted to the tap water most beginners would use in their new tank. However, Bettas naturally originate from soft waters with high acidity and tend to do better, and live longer in aquariums with such conditions.
My Closing Thoughts
It might feel overwhelming trying to figure out what type of water fits best with the aquarium you want to create.
When things seem complicated, try to keep them simple. In my personal opinion, it’s best to stick with what works.
Spring water is a great choice for multiple reasons, but if that doesn’t work for you, tap water is another viable solution.
Continue to research to figure out what works best for you and your finned friends.