How Long Does Water Conditioner Take to Work for Aquariums?

Updated on by Patrice Alsteen | Affiliate links may be present.

You want your fish to live a happy, healthy life! Unfortunately, it is not as easy as simply plopping fish into a tank full of tap water. Tap water contains chlorine, chloramine, and heavy metals that can be harmful to fish.

What is a water conditioner, anyway? How long after the water is conditioned before it is safe to add your fish? Keep reading to find out!

What is Water Conditioner?

Aquarium water conditioner removes chlorine and chloramine from tap water. Often, the active ingredient is sodium thiosulfate. The sodium thiosulfate may cause a slight ‘rotten egg’ odor in the water. This is normal for any sulfate compound.

Sodium Thiosulfate has a chemical reaction with chlorine, removing the chlorine almost immediately. Some water conditioners also contain electrolytes and aloe vera to help coat the fish and protect them from other harmful elements.

Most tap water contains up to 4 milligrams of chlorine per liter of water. This amount of chlorine will make fish sick, or even kill them. An acceptable level of chlorine for healthy fish is 3 micrograms per liter. A water test kit may be helpful to make sure that your aquarium water is at the right levels for healthy fish.

How Long Does it Take for Water Conditioner to Work?

A water conditioner removes chlorine almost immediately. Once the conditioner comes into contact with each water molecule, the chlorine is removed. It may take a while to ensure that all the conditioner has permeated all of the water.

Make sure to read all the instructions on the water conditioner you choose. Different brands and formulas require different amounts of conditioner per liter of water.

Generally, most water conditioners only take about 15 minutes to remove the chlorine from tap water.

How Can I Speed Up the Water Conditioning Process?

Aerating the water once the conditioner is added will help the conditioner reach every water molecule!

Place the water and the conditioner in a clean container. Aerate the mixture by stirring the conditioner into the water for 5-30 minutes. This is enough time for the conditioner to remove all traces of Chlorine.

Can I Remove Chlorine Without a Water Conditioner?

It is possible to remove chlorine from your aquarium water without a water conditioner.


Chlorine evaporates into the air. If you allow your aquarium full of tap water to sit, the chlorine will eventually evaporate into the air, and the water will be safe for fish.

How long does it take chlorine to evaporate? The general rule of thumb is that it takes 110 hours for 2 PPM of chlorine to evaporate from 10 gallons of water.

If you don’t want to do the math, most of the chlorine should evaporate from your fish tank in 24-48 hours. If you are still nervous about potential chlorine levels, test the water after 48 hours, or leave the tank for 4-5 days.

Carbon Filter

A carbon filter will filter out both chlorine and chloramine. The activated carbon in the filter absorbs harmful chemicals in the water.

Final Thoughts

A water conditioner is a simple way to remove chlorine and keep your fish healthy. Use a water conditioner whenever you replace water, clean the tank, or add a new fish.

About Patrice Alsteen

Patrice has been an animal lover, right from her childhood. She's currently enjoying the company of her cat, dog, aquarium fishes, and a few small furry companions.

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