Water Dechlorinator: How It Works and How Much to Use in Aquariums

Many fishkeepers are unclear about water conditioners for aquariums – how they work, potential risks from overdosing, and the differences amongst the many brands of dechlorinators. Based on the available research and our years of experience using them, let’s talk about the truth behind water conditioners and answer your frequently asked questions.

Do Fish Really Need Water Conditioner?

Maybe. If your drinking water comes from a municipal water supply or other public water system, then most likely it is disinfected with chemicals like chlorine or chloramine to eliminate bacteria, viruses, and other microorganisms that can cause diseases. These chemicals can be toxic to aquatic animals as well as beneficial bacteria, so they must be removed using a dechlorinator. You should add water conditioner to tap water to prevent your fish from getting burned. This could lead to them gasping heavily or gasping for air.

Water conditioner may not be necessary if the water is from a well or another water source that isn’t treated with chemicals. You should have your well water tested for heavy metals. Some dechlorinators may be able to help.

Does letting water sit remove chlorine? Yes, chlorine is fairly unstable and will gradually evaporate from water. Many water treatment plants now use chloramine as a disinfectant instead of chlorine. It is made by mixing ammonia with chlorine. Chloramine cannot be easily removed from water via evaporation and must be neutralized using dechlorinator. To ensure that your tap water does not contain chloramine but chlorine, you can allow the water to sit for between 1 and 5 days. This will allow the chlorine to evaporate. You can speed up the process by heating the water for about 15-20 minutes or aerating it with an airstone for 12-24hrs. Multi-test strips can be used to test the water for chlorine and measure it.

An air pump and an airline tube are connected to air stones. They inject water into the water and agitate it. This speeds up gas exchange.

What does a Dechlorinator do?

Water conditioners are used to reduce chlorine and chloramine in water and make it safe for fish to drink. Most dechlorinators have sodium thiosulfate. It reacts to chloramine and chlorine to produce harmless byproducts. Sodium Thiosulfate is often dissolved into water to make liquid dechlorinators. It looks similar to rock salt or white powder. Some water conditioners include pH buffers and aloe vera to aid in the healing of fish’s slime coats.

Does a dechlorinator have ammonia removal? According to the packaging, some do. Dechlorinators can only react to chloramine’s chlorine component when used to treat the substance. Fish are unable to ingest the remaining ammonia ions in the water. Some dechlorinators, such as Fritz Complete Water Conditioner and Seachem Prime, contain additional chemicals that temporarily lock the ammonia into an inert (i.e. ammonium) state for up to 24 hours. During this time, the ammonium can be consumed and further broken down by beneficial bacteria in your aquarium and filter.

All dechlorinators neutralize chloramine and chlorine, but some have additional chemicals to deal with ammonia and nitrite.

Can dechlorinator remove bleach quickly? The amount and concentrations of bleach used determine how much dechlorinator is required. After the Purigen chemical filter media has been washed in bleach, please refer to these instructions for neutralizing it.

Are Fish harmed by Dechlorinator?

In general, it is not. There are rare cases that it can be dangerous. In order to remove chlorine from the water, the reducing agents in a dechlorinator consume oxygen. This could make it dangerous for tanks that are not well oxygenated. For instance, goldfish and discus aquariums can require huge 90% water changes. If your water has low oxygen content, you can add lots of dechlorinator to further reduce the oxygen. This could potentially cause fish death and harmful bacteria.

To prevent this, most fishkeepers increase surface agitation in the aquariums to increase gas exchange. This refers to the process by which carbon dioxide (CO2) is expelled and new oxygen is added to the tank. Hobbyists who have high-tech planted aquariums that use pressurized CO2 will often try to reduce surface agitation. The intent is to decrease gas exchange so that more CO2 stays in the water for the plants to use. This is in addition to the fact that plants only consume carbon dioxide during the day and then consume oxygen at nights. If you water change your water in the early morning, right before the lights go on, the dissolved oxygen will be at its lowest level. Adding low-oxygen water and dechlorinator could be a recipe for disaster for your aquatic animals.

How Much Dechlorinator Should I Use per Gallon?

Every dechlorinator is different, so follow the dosing instructions on the package. Fritz Complete, for example, recommends 1 ml per 10 gallons water. This is because different cities use different amounts. How can you tell what the best concentration is for your water? Because the manufacturers of dechlorinators don’t know what chlorine is used in your area, they have made general guidelines that should hopefully be sufficient to cover tap water.

Fritz Complete comes with an easy-to-use pump head for dosing 1 ml of dechlorinator per 10 gallons of water.

How much time does it take for the dechlorinator work? Most companies state that the dechlorinator should be added to the tap water in a separate container. That being said, we always add the water conditioner directly to the aquarium and then pour in fresh tap water, and there have never been any problems.

Is it possible to put too much chlorine in your fish tank? Fritz Complete allows you to treat very high levels of nitrite and chloramine within 24 hours. This is a very large range that allows much room for error. Just keep in mind that potent concentrations of dechlorinator will quickly reduce the amount of dissolved oxygen, so it may be best to add an air stone for the next 3-4 hours to increase oxygenation in the water.

It would be smart to research the average chlorine use in your area and do some experiments at home. Let’s assume your town uses 2 parts per million (ppm) of chlorine. What happens if you do an average 30% water change for a 100-gallon aquarium, and then add 3 pumps Fritz Complete to 30 galallons of tap water? Does the chlorine test register at 0 ppm? Do you have to use more water conditioner to get rid of all the chlorine? Keep it simple: Make sure you test your water and make sure that you don’t use too much dechlorinator.

A multi-test strip is used to quickly determine how much chlorine your water contains.

Many people ask us for recommendations on the best dechlorinator. In truth, Fritz Complete Water Conditioner is our favorite because it has a super simple pump head that can treat 10 gallons per squirt. There’s no need to carefully measure the volume of liquid in a cap or pour it into a bottle. You can do it in just a few seconds.