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Preparing Your Tap Water for Aquarium Use

(The First Tank Guide)

I frequently get questions about dechlorination. What is a dechlorinator, where do I get a dechlorinator, what dechlorinator do I use, etc.

What Is a Dechlorinator?

A dechlorinator, sometimes referred to as a chlorine neutralizer or a chlorine remover, is a chemical additive that renders the chlorine and chloramine in your aquarium source water harmless to your fish and biological filter.

Dechlorinators fall into the general category of 'water conditioners,' though dechlorinators are probably about the simplest water conditioners. Remember, though a dechlorinator is a water conditioner, not all water conditioners are dechlorinators.

Why Do I Need a Dechlorinator

Most (if not all) municipal water supplies are treated with chlorine, chloramine, or both. Often holding tanks for wells in rural communities, farms, and ranches are are also similarly treated. These chemicals are necessary to kill off any harmful bacteria or other pathogens which get into the water.

Though the dosages of these chemicals in the water supply are low enough that they are not harmful to land animals (including people, dogs, cats, hamsters, horses, etc) or house plants, they are high enough to cause damage to your biological filter. This damage will allow ammonia to start to build up in the tank, eventually becoming harmful to your fish. For this reason it is important that you treat your water to remove chlorine with an appropriate dechlorinator before you add it to your tank.

How Much Is a Dechlorinator Going to Cost?

Dechlorinators are very inexpensive. Usually for just a few dollars you can get enough to treat your tank for a year or more. However, if you use some of the more expensive dechlorinators, you will have higher dosages and higher cost, so you will not be able to treat as much water for the same amount of money. For a regular dechlorinator, you should be able to get enough to treat 4,000-5,000 gallons of water (16,000-20,000 liters) for $5.00-$10.00.

Where Can I Get a Dechlorinator?

You should be able to get a dechlorinator from your local pet shop. Most stores carry a variety of dechlorinators to meet the varying needs of their customers. Some customers want different additives or benefits from their dechlorinator, while others just want a basic chlorine neutralizer. In my experience, though there are rare exceptions where you may want extra additives, like stress relievers, skin tonics, aloe extract, or vitamin E, these are generally unnecessary and only increase the expense of dechlorinating your aquarium, while making the process of dechlorinating your aquarium more expensive.

How Do I Use a Dechlorinator

Each dechlorinator is slightly different in dosage recommendations, so you need to refer to the label on the dechlorinator you have purchased. However, most of the good dechlorinators - that don't do a lot of unnecessary extra stuff - are dosed between one drop for each two gallons of water an two drops for each gallon of water (that's between about 1 drop for each 8 liters and one drop for each 2 liters). Some of the other water conditioners are dosed at 1/2 teaspoon for each ten gallons to 1 Tablespoon for each ten gallons (that's about 2.5-15ml for each 38 liters).

Remember, though, you only need to treat the new water you are adding to the tank, you do not need to treat the entire tank volume unless you are filling the tank for the first time, or have drained all the water from the tank for some reason.

Dechlorinators are also generally very fast acting. Most will neutralize the chlorine in a bucket of source water in a minute or two, and will neutralize chloramine in as little as five minutes.

Remember to check the directions on the chlorine remover you choose to use and make sure you follow those instructions. These will tell you both how to dose the dechlorinator and how long it should take to be effective.

What Are the Side Effects of Using a Dechlorinator?

Dechlorinators are designed to remove chlorine and/or chloramine from your source water. Ideally, they should not have a bearing on water chemistry and should not impact other additives you are using. However, the more "extra stuff" your dechlorinator does, the more likely some kind of issue could come up.

One common problem that occurs with some of the "fancier" dechlorinators, is that they can leave a buildup over time. This is particularly of concern in small tanks or bowls, in tanks where the product has been over used, or in tanks with insufficient filtration. Keeping your fish in a large enough tank, keeping the tank well filtered, and being careful not to overdose the water treatment can help alleviate this - or you could just use a regular dechlorinator without unnecessary additives.

I have also had some issues with some of the "fancier" dechlorinators in tanks with reptiles or amphibians (frogs, turtles, newts, salamanders, etc.), and with other "fancier" dechlorinators in tanks with invertebrates (crayfish, lobsters, shrimp, snails, etc.). My recommendation in this case would be to use a regular dechlorinator without unnecessary additives.

What Do I Need to Be Aware of When Choosing a Dechlorinator

All dechlorinators will remove chlorine (I can't think of one that doesn't), a few do not neutralize chloramine. If your source water is treated with chloramine, make sure you get a dechlorinator that will remove this chloramine from the water. A dechlorinator that does not neutralize the chlorine in chloramine will likely be labeled as such, but it may be in the fine print. Your local pet shop should know if your water is treated with chloramine or not.

Another thing to watch for is unnecessary ammonia removers in some chloramine removers. Ammonia removers can cause problems for your biological filter, and should be avoided. Look, instead, for a dechlorinator that removes chlorine and chloramine and doesn't have other 'benefits.'

Can't I Just Leave the Water Out Overnight?

Chlorine is very volatile, so it will evaporate very quickly from your source water. If your water is only treated with chlorine, then letting it stand over night should allow the chlorine to evaporate from the water and make it safe to use. In fact, you can even speed this up by bubbling air through the water with an air stone. This will increase the surface area of the water and allow the chlorine to evaporate even faster.

However, this is one of the primary reasons for switching form chlorine to chloramine treatment of water supplies. Unlike chlorine, chloramine is non-volatile. It doesn't evaporate quickly. If your source water is treated with chloramine, it is important that you get a dechlorinator that will neutralize the chlorine in chloramine.

Also, if you can use your water quickly after drawing it, you can use water that is closer to the correct temperature, rather than water that is room temperature. This will reduce the risk of temperature shock to your fish, plants, biological filter, and other critters in the tank.

Remember, dechlorinating your source water is cheap, easy, fast, and could definitely save the lives of your fish...

"I think you[r] info is brilliant and very interesting."
October 21, 2008
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"My 3 year old daughter desperately wanted a fish so the family troops off to the pet store and buys - you guessed it - painted glass fish. I thought, "Wow, pretty fish." [It] never occurred to me the terrible things that are done to make them look like that. Now after [an] awful heart-wrenching morning explaining to my daughter her fish is in heaven with God, after only a week, I decided to look up these fish and see what I did wrong. Well I figured it out, my mistake was not researching what fish I was buying. A hard lesson learned at the expense of my daughter. I will never understand how people can justify hurting another creature solely for profit. Thanks for all the info on these lovely but mistreated little fish."
March 22, 2003
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