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.

Does Fish really need water conditioner?

Maybe. It is possible. These chemicals are harmful to beneficial bacteria and aquatic animals, and must be removed from the drinking water by 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 even stopping breathing.

Your aquariums will not require water conditioner if you have water from a natural well. 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. However, many water treatment plants have begun using chloramine instead of chlorine because it is a more stable disinfectant formed by combining ammonia and chlorine. Chloramine cannot be easily removed from water via evaporation and must be neutralized using 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. For a faster evaporation, you can either aerate the water using an air stone for 12-24hrs or boil the water in a kettle for 15-20 minutes. Multi-test strips can be used to test the water for chlorine and measure it.

Air stones can be connected to an aircraft tubing and an air pump to inject air into the water. The water will then surface agitated and gas exchange is increased.

What does the Dechlorinator do for you?

Water conditioners serve two purposes. They break down chlorine and chloramine to make water safe for fish. Almost all dechlorinators contain sodium thiosulfate, which reacts to chlorine and chloramine to form harmless byproducts. Sodiumthiosulfate can look like rock salt and white powder. It’s often dissolved in water to make liquid chlorineizers. Water conditioners may contain pH buffers, aloe verde to heal fish slime coats, and other additives.

Does dechlorinator remove ammonia? Some of them do, as stated on their packaging. Dechlorinators can only react to chloramine’s chlorine component when used to treat the substance. The remaining ammonia ions left in the water are toxic to fish, so some dechlorinators – such as Fritz Complete Water Conditioner, Seachem Prime, and Kordon AmQuel – contain extra chemicals that temporarily lock up the ammonia into an inert state (i.e., ammonium) for up to 24 hours. The ammonium can be consumed, and then further degraded by beneficial bacteria within your aquarium or filter.

While all dechlorinators neutralize the chlorine and chloramine, some include extra chemicals to remove ammonia, nitrogen, and heavy metals.

Will the dechlorinator neutralize bleach? The dechlorinator reacts to bleach to remove it faster. 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.

Is the Dechlorinator harmful to fish?

Generally speaking, no. It is not dangerous in most cases. The chlorine reducing agent in the dechlorinator uses up oxygen, which can make it hazardous for tanks with low oxygen. Goldfish and discus aquariums, for example, can need large water changes of up to 90%. If your water has low oxygen content, you can add lots of dechlorinator, which will further reduce the oxygen available to your fish and beneficial 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. 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 morning, right before the lights go on, the water’s dissolved oxygen will be at its lowest level. A low-oxygen water source and dechlorinator can spell disaster for your aquatic pets.

How much dechlorinator should I use per gallon

Each dechlorinator has its own dosing requirements, so make sure to follow them. Fritz Complete recommends that you use 1 ml dechlorinator for every 10 gallons. What makes these directions a little confusing is that different municipalities use different amounts of chlorine in their water, so how do you know what is the right concentration for your water? Since the dechlorinator manufacturers do not know how much chlorine your town uses, they deliberately make general guidelines that will hopefully cover everyone’s tap water.

Fritz Complete contains an easy to use pump head for dosing 1ml of dechlorinator in 10 gallons water.

How fast does the dechlorinator start to work? Because it takes between 2 and 5 minutes for chlorine or chloramine to neutralize, many companies advise that you use a separate container to add the dechlorinator water 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.

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 range is very wide and allows for a lot of room for error. Remember that high concentrations of dechlorinator can quickly reduce the amount dissolved oxygen. It is best to add an oxygen stone to the water for the next 3-4 hour to increase oxygenation.

It is a good idea for you to check the chlorine usage in your locality and make some home experiments. Let’s say you find out your town uses 2 ppm (parts per million) 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? Can you get away with less water conditioner, or do you need to dose more pumps to completely eliminate the chlorine? The bottom line is to test your water for the lowest amount of chlorine and ensure that your fish have enough oxygen.

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

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. Just a few quick pumps and you’re done.