Chlorine and its cousin, chloramine are deadly to fish. You must safely remove chlorine for fish safety. Since these deadly compounds oxidize and literally burn organic material on contact, either will immediately cause damage to tender membranes such as gills if it contacts them.
The very best method to prevent this disaster is to always ensure neither compound ever has any opportunity to contact the fish in any way at all.
Since chlorine treatment is done by the water company - before it is delivered to your tap, simply dumping new water into an established aquarium is a recipe for disaster.
Never, ever, ever do it!
The best and most highly recommended method is to treat the water before it has any chance to come into contact with the aquarium itself to safely remove chlorine.
|My personal choice for water conditioner is "Nutrafin Aqua Plus Tap Water Conditioner" because it removes both chlorine and chloramine from tap water. Chelates heavy metals, coats the fish, as well as some other nice things. It's my favorite.|
That means that the best place to neutralize it is in the transport method between tap and tank. That really is not much of a problem since new water is normally transported using a bucket.
Since the chemical reaction between the active ingredient of most water conditioners and chlorine removers acts instantaneously, there is no danger of allowing any chlorine into the aquarium if you simply treat the new water when it is in the transport container.
We recommend the following procedure to safely remove chlorine when replacing evaporated water, or the water removed during a partial water change.
The absolute safest method of doing this is:
1) Run the tap for a minute or so to allow any metallic ions in the standing water deposited by metal pipes to be flushed down the drain before the water starts to fill the bucket.
2) At this time, it is also wise to regulate the temperature somewhat close to the aquarium temperature to reduce any thermal shock as well.
3) Once the bucket is placed in position to fill, dose the appropriate amount as the water fills the bucket.
4) Transport the water in the bucket to the tank, by adding the water conditioner to the bucket as it begins to fill, there is no chance that it was not thoroughly mixed with the new water from the tap. So it is safe and ready for fish when you pour it into the tank.
To be honest, we are always quite liberal with the dosage, twice the dosage does not cause any harm, or a moment's hesitation, and ensures that the chlorine, even if the water company added lots extra, will not get through to harm the fish. Most of the water conditioners also have many added features that are meant to help the fish with the stress and dangerous metals. Even these are provided in amounts where they cannot hurt the fish or the other inhabitants of the aquarium; such as bacteria and plants, but rather are there to ensure they continue to thrive over time.
Tests of some of the products have shown that the products are safe for fish at 100 times dosage!
Never use less than recommended dosage, but if you end up overdosing somewhat, do not worry. It won't hurt anything and prevents a very serious problem from happening. We never add untreated tap water to an established tank, even if the water conditioner is already placed directly in the tank.
Usually the dose is for the replacement volume and there may be a slight lapse between the chlorine hitting the aquarium and the neutralization process.
If at all possible treat in the bucket, never directly in the tank, this reduces the chance of unseen damage to gills that can cause serious health problems later in the fish's life.
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Beginning Aquarium Tips