Water Dechlorinator: how it Works and how much to use In Aquariums

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 years of experience with them and the research available, let’s get to the bottom of water conditioners.

Does 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 are toxic to aquatic animals and beneficial bacteria and therefore must be removed from the water 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.

Your aquariums might not require water conditioner if your water comes from a well, or any other source of water that has not been 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. It is difficult to remove chlorine from water by evaporation. Instead, it must be neutralized with a dechlorinator. If you are sure your tap water contains chlorine and not chloramine, you can let the water sit for 1-5 days to allow all the chlorine to evaporate. The evaporation process can be accelerated by boiling the water for 15-20 minutes, or using an air stone to aerate it for 12-24 hours. Use multi-test strips to measure the water and make sure no chlorine is left.

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. Nearly all dechlorinators include sodium thiosulfate. This reacts with chlorine and chloramine to create 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 contain pH buffers, aloe vera to help heal the fish’s slime coats, or extra additives.

Does dechlorinator remove ammonia? Some of them do, as stated on their packaging. This is due to the fact that dechlorinators only react to the chloramine part of chloramine when they are used to treat it. Fish can be poisoned by the ammonia ions that remain in the water. Therefore, some dechlorinators such as Fritz Complete Water Conditioner or Seachem Prime contain extra chemicals that temporarily store the ammonia in an inert state (i.e. the ammonium) for up 24 hours. The ammonium can be consumed, and then further degraded by beneficial bacteria within your aquarium or filter.

All dechlorinators neutralize chlorine and chloramine, but some contain extra chemicals to treat ammonia, nitrite, and heavy metals.

Will the dechlorinator neutralize bleach? The dechlorinator reacts to bleach to remove it faster. The bleach concentration and amount used will determine the amount of dechlorinator required. You can start by reading the instructions to neutralize Purigen chemical filters media after it has been soaked in bleach.


Is the Dechlorinator harmful to fish?

In general, it is not. However, there are some rare, one-off cases where it could be potentially dangerous. The reducing agents in dechlorinator use up oxygen when removing chlorine from the water, and this reaction could be hazardous in poorly oxygenated tanks. Goldfish and discus aquariums, for example, can need large water changes of up to 90%. If you are using water with low oxygen content, adding lots of dechlorinator will further deplete the available oxygen, which can potentially suffocate your fish and beneficial bacteria.

Most fishkeepers try to prevent this from happening by increasing surface agitation in their aquariums to improve gas exchange – the process in which carbon dioxide (CO2) exits and fresh oxygen enters the tank water. Hobbyists using high-tech, planted aquariums that infuse pressurized carbon dioxide (CO2) often want to reduce surface agitation. The intent is to decrease gas exchange so that more CO2 stays in the water for the plants to use. Combine this with the fact that plants only consume CO2 during the daytime and then they consume oxygen at night. 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. Your aquatic animals could become sick if you add low-oxygen water or a dechlorinator.

What is the recommended amount of dechlorinator per gallon?

Each dechlorinator has its own dosing requirements, so make sure to follow them. As an example, Fritz Complete calls for 1 ml of dechlorinator per 10 gallons of water. These directions are a bit confusing because different municipalities use different amounts. So how can you determine the correct concentration 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 long does dechlorinator take to work? Many companies recommend that you add the dechlorinator directly to tap water in separate containers before adding it to your aquarium. 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.

Do you think you have too many dechlorinators in your fish tanks? Fritz complete allows you to dole out up to five times the recommended dose within 24 hours. This is a large range, so there’s a lot of room to make mistakes. Keep in mind that dechlorinators with high concentrations can quickly decrease the amount of dissolved O. For this reason, it is a good idea to add an airstone for 3-4 hours to increase the oxygenation of the water.

It wouldn’t be a bad idea to look up the average chlorine usage for your municipality and run a few experiments at home. Let’s say you find out your town uses 2 ppm (parts per million) of chlorine. If you do a 30% water change on a 100-gallon aquarium and you dose 3 pumps of Fritz Complete into 30 gallons of tap water, does the chlorine test register as 0 ppm? Is it possible to do without water conditioner or to eliminate all chlorine completely? Keep it simple: Make sure you test your water and make sure that you don’t use too much dechlorinator.

Use a multi-test strip to quickly measure how much chlorine is in your water.

Many people ask for our recommendation on the best dechlorinator to use, and honestly, we prefer Fritz Complete Water Conditioner because of the super easy pump head that treats 10 gallons of water per squirt. There’s no need to carefully measure the volume of liquid in a cap or pour it into a bottle. Just a few quick pumps and you’re done.