You can use spring water in a fish tank, but it is not a good idea — unless you are trying to lower the pH or hardness of your aquarium water.
Even if you are using spring water for a specific reason, you must test and treat the water before adding it to your fish tank. Please be careful, as each brand of spring water has different minerals and pH levels, and some spring water contains chlorine and other chemicals.
Be mindful. When misused, spring water can harm your fish.
Is Spring Water More Acidic?
Spring water comes from a variety of different springs, some of which are more alkaline (basic) and some of which are more acidic.
Bottled spring water tends to be more acidic than other kinds of water. This is not good for freshwater fish, who tend to live in neutral aquatic environments.
If your aquarium becomes too alkaline, you can use more acidic spring water if you test and treat the new water first.
Do not place a fish directly into overly acidic spring water as low pH can lead to illness, injury, and death.
Can You Put Bottled Water in a Fish Tank?
No. Because bottled water is designed for human consumption, it usually contains chemicals. While chlorine can help clean and preserve drinking water for us, it can hurt freshwater fish.
Additionally, bottled water tends to be filtered, distilled, or enhanced, so it may not have the nutrients fish need. Worse, it may be polluted with dyes, flavors, extra mineral content, heavy metals, or other unhealthy additives for fish.
Of course, you can put bottled water in a fish tank if the water is designed and bottled for fish. Many manufacturers sell betta water, for example, pre-treated water designed to meet bettas’ preferred water parameters.
How Do You Make Bottled Water Safe for Fish?
If you have no other option and need bottled water, you can make it safe for your fish using a store-bought water conditioner.
Depending on the brand, you may also need to remineralize the water with mineral drops or trace amounts of Himalayan sea salt.
Do You Need to Condition Spring Water for Fish?
Yes. If you decide to use spring water in your fish tank, you must test and condition it first.
Test spring water for its pH and hardness; if these parameters are correct, use a water conditioner to neutralize chlorine and other chemicals.
Never put any water in your fish tank before testing and conditioning it. The only exception is pre-conditioned water made specifically for your aquarium.
Can Spring Water Kill Fish in a Fish Tank?
Yes. Left untreated, spring water can kill fish in a fish tank.
Water that is too acidic can burn your fish’s skin and scales and lead to a slow, painful death.
Chemicals like chlorine can make your fish very sick, and untreated spring water may also contain bacteria, fungi, and parasites that can cause illness.
Using spring water in a fish tank is risky, so most fish keepers prefer to avoid it altogether.
Can Purified Water Kill Fish in a Fish Tank?
All kinds of “purified” water can kill fish in a fish tank. Chemicals used in the purification process are safe for humans to drink, but they can quickly harm or kill freshwater fish.
What Is the Best Water To Use in a Fish Tank?
Generally, treated tap water is the best water to use in a fish tank. Only the pre-conditioned aquarium water sold at pet stores is safer.
In addition to being dangerous for your fish, spring water, purified water, and bottled water are expensive. If you spend the money, you might as well purchase pre-treated fish tank water at the pet store instead.
Otherwise, tap water and a store-bought water conditioner is the safest, most cost-effective option.
What Fish Can Live In Tap Water?
Most freshwater fish can live in tap water if you treat it with a water conditioner first. Some popular examples include:
Remember, no matter how hardy the species, you should always treat your tap water (and cycle your aquarium) before introducing a fish to your tank.
Some varieties of fish can survive untreated tap water, but none of them will thrive.
How Long Can Fish Survive In Tap Water?
The chlorine in untreated tap water can destroy a fish’s slime layer in about 30 seconds, meaning fragile fish will be without defenses. A fish without defenses will only last for a few hours.
Other fish may survive the initial shock of tap water, but the experience may shave years off their lifespans.
As we said, some fish can survive in tap water, but few can thrive.
Conditioning tap water does not take very long, and fish can survive their entire lives in treated, properly maintained tap water.
Once you condition the water in your aquarium and get the nitrogen cycle going, the fact that you built your aquarium with tap water won’t matter!
Don’t Bother With Bottled Water!
Spring water from a natural, underground water source may sound luxurious and refreshing, but it is not good for your fish. It may be too acidic, have the wrong minerals, or contain other contaminants, especially if bottled for human consumption.
People may drink from clean, crisp springs or bottles imported from Fiji, but freshwater fish usually live in ponds, lakes, streams, and even rice paddies, so you and your fishy friends have different needs.
You can honor these needs by testing and conditioning any water you choose. We recommend pre-conditioned aquarium water or using tap water so that you treat yourself at home.
If necessary, you can use spring water or bottled water — just make sure you treat it using a store-bought water conditioner and get your tank cycled as soon as possible.
Put simply, treated and tested spring water will not kill your fish, neither will treated bottled water, but untreated water can and will harm your fish.
Avoid spring water and bottled water whenever possible, and always test and condition your aquarium water before adding it to your tank.