In case you have ever used tap water to fill your aquarium, you have most likely seen something odd. Your fish might get stressed out, lethargic, or even ill shortly after. Why? Chlorine or chloramine is present in most tap water and is lethal to aquatic organisms.
Although not harmful to humans in low concentrations, chlorine is lethal to fish. This is the reason why one of the first and most important tools every aquarist needs to utilize is a dechlorinator.
We will look into why dechlorinated water is imperative to the health of your fish, the mechanism of action of dechlorinators, and how to safely condition your water using reliable products such as AquaVitals products.
What Is Chlorine Doing in Your Tap Water?
To eliminate dangerous bacteria, most cities put chlorine or chloramine in the drinking water. This makes the water drinkable. Sadly, it also makes it unsafe for aquatic life.
Chlorine is a powerful chemical. It decays and destroys cell membranes. On exposure to it, fish have their gills scorched, their slime coat damaged, and they can even gasp at the air-water interface.
Fish can be significantly stressed or die due to low concentrations of chlorine. What is the good news? A proper dechlorinator will easily correct it.
What Does a Dechlorinator Do?
A dechlorinator is a water conditioner that neutralizes chlorine and chloramine, making tap water safe for your fish. It works instantly and is easy to use. Just add the recommended dose to your tap water before pouring it into your tank.
Most modern dechlorinators also detoxify heavy metals and bind harmful compounds like ammonia. This added benefit makes them useful not only during water changes but also in emergencies, such as ammonia spikes.
For example, AquaVitals Nitrifying Bacteria pairs well with a dechlorinator. Once chlorine is removed, beneficial bacteria from AquaVitals can thrive and start breaking down waste in the tank. This boosts your tank’s natural filtration system.
Why Fish Need Dechlorinated Water
Fish breathe by passing water through their gills, pulling out oxygen and releasing carbon dioxide. Chlorine damages this delicate gill tissue, making it difficult for fish to breathe. In some cases, exposure to chlorine or chloramine causes gill inflammation, lethargy, or sudden death.
Young fish, fry, and sensitive species are even more vulnerable. So, if you’ve invested in a planted tank or are keeping delicate species, a dechlorinator isn’t optional—it’s essential.
A good rule to follow: Always treat your water before it goes into the tank. Don’t wait for the fish to show signs of stress.
How Long Can Fish Survive in Chlorinated Water?
Not very long. Some hardy fish may last a few hours, but most will become visibly stressed within 30 minutes. Gasping at the surface, darting around the tank, or sitting motionless are all signs of trouble.
Prolonged exposure leads to respiratory distress, burns on the gills, and compromised immune systems. If you’ve already added untreated tap water by mistake, act fast. Perform a partial water change and use a dechlorinator immediately.
Products like AquaVitals Stress Shield can also help reduce the shock and allow fish to recover faster. It calms the fish and helps restore their protective slime coat.
Don’t Forget Chloramine
Many water treatment plants now use chloramine, a combination of chlorine and ammonia. It stays stable longer in pipes and is harder to remove.
Unlike chlorine, chloramine doesn’t evaporate easily. Even if you leave the water out overnight, it will still remain. Basic water conditioners may not be enough—choose a dechlorinator specifically labeled for chloramine.
To deal with the residual ammonia left behind after neutralizing chloramine, it’s wise to add AquaVitals Nitrifying Bacteria. This jumpstarts the nitrogen cycle and helps convert ammonia into less harmful compounds.
When Should You Use a Dechlorinator?
Use it every time you:
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Add new water to your tank (even top-offs)
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Set up a new aquarium
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Do partial or full water changes
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Clean filters or decorations using tap water
Don’t guess—test. Use a chlorine test kit to check your tap water if you're unsure. It's also good practice to test your tank after treatment to ensure levels are safe.
Once treated, your water is safe for fish, shrimp, and plants. Dechlorinators also protect beneficial bacteria in your filter from being destroyed.
Supporting a Healthy Tank
Once your water is chlorine-free, you can support long-term health with the right care:
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Use AquaVitals Fish Food to feed your fish with minimal waste.
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Boost your plants using AquaVitals AquaCarb or Macro/Micro Nutrients to keep water conditions balanced.
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Use AquaVitals Root Tabs for planted tanks, helping plant roots thrive and naturally outcompete algae.
Healthy plants, healthy water, and healthy fish all start with safe water. And safe water begins with a reliable dechlorinator.
Final Thoughts
Chlorine and chloramine are silent threats in every drop of tap water. But with a trusted dechlorinator, you can make your aquarium a safe and healthy home. Whether you're changing water or setting up a new tank, always treat your water first.
AquaVitals offers science-backed solutions that protect your fish from stress and harm while supporting a thriving aquatic environment.
Clean, dechlorinated water is the foundation of every successful aquarium. Don’t skip this step—your fish are counting on you.
Frequently Asked Questions
1. What is the purpose of a dechlorinator?
A dechlorinator neutralizes harmful chlorine and chloramine in tap water. It makes the water safe for fish, shrimp, and beneficial bacteria, and should be used during every water change.
2. Why do fish need dechlorinated water?
Fish gills are sensitive. Chlorine damages them and makes it hard to breathe. Dechlorinated water keeps fish stress-free, helps them stay healthy, and prevents long-term issues or sudden death.
3. Why is chlorine bad for fish?
Chlorine burns fish gills and skin, weakening their immunity and causing breathing problems. Even low levels can trigger stress or illness. It also harms beneficial bacteria in your aquarium filter.
4. How long can fish survive in chlorine water?
Most fish show signs of distress within 30 minutes. Prolonged exposure can lead to severe injury or death within hours. Quick action and dechlorination are critical to saving them.
5. How to dechlorinate water?
Use a liquid dechlorinator according to label directions. Add it to tap water before introducing it to your tank. For chloramine, use a conditioner that treats both chlorine and ammonia.