How to Remove Chlorine from a Pond to make it Safe for Fish.

If you have a garden pond, especially a new pond, you need to remove the chlorine that is present when filling the pond with tap water.

De-chlorination should be your top priority if you want to make a safe home for your fish to live in.

Simply filling a new pond or even topping up a pond after a partial water change with tap water will not end well if you don’t treat it in some way.

The problem with tap water is it has chlorine or chloramine added to it, they are added to make the water safe for humans to drink, unfortunately even low levels of chlorine or chloramine can be extremely toxic to fish.

Chloramine is used by some water authorities as a replacement to chlorine, in this article is we talk about chlorine but the advice is the same for chloramine.

Chlorine is added to water to kill parasites and bacteria, it also removes bad odours, its like a disinfectant for mains water.

So why is chlorine bad for fish.

As you might of gathered, chlorine is really bad for fish, but it’s not only fish that suffer, plants can too.

Let’s get this straight, chlorine kills fish, it damages their gills, scales and their breathing tissue.

It’s not a nice death, first the chlorine burns the fish on the outside, then as it passes through their gills it enters their digestive system which burns them from the inside and it can kill them really fast.

Not only is it bad for fish and plants, it’s bad for your pond, if you have an established pond it will kill of all the good bacteria that remove harmful toxins in the pond, if this happens and you still have fish that have just about survived the chlorine, the ammonia and nitrate build up will certainly kill them off.

Removing chlorine from water.

There are three methods you can use to remove chlorine from tap water, natural, chemical and mechanical.


Letting the water stand for about 48 hours will allow the chlorine in the water to evaporate into the atmosphere.

The biggest drawback to this method is the time it takes, there are a few things that you can do to speed things up.

Rather than having water in buckets use shallow containers, this will increase the amount of surface area exposed to the air.

This only works if you are topping up your pond water, imagine how many buckets you would need to fill up a new pond.

If you are filling up a new pond use a submersible pond pump to bring the water from the bottom of the pond to the surface.

You can also use an air pump to take the air to the bottom of the pond.

The good thing about this method is its free to do, but you must test the water to make sure the chlorine has gone and the water is safe for fish.


Water conditioners: this is probably the most common method used to remove chlorine from tap water.

These treatments can be used as many times as it takes to get the chlorine levels right and can be used in small and large ponds.

For a new pond with 100% tap water this is the perfect solution, they can also be used in a partial water change without affecting the ecosystem too much.

If you’re adding tap water to top up an established pond the water can be treated in a bucket first and then added to the pond.

A couple to go for would be the Blagdon tap water fresh start, you can purchase it from or the Tetra AquaSafe also available from

While this is good method for speed it is more expensive than letting the chlorine evaporate naturally.


A simple solution is to mechanically remove chlorine from the tap water with an in-line dechlorinator.

They use a carbon filter to remove the chlorine from the water coming through your hosepipe before it enters the pond.

You connect the filter in-line to your hosepipe using connectors and just turn on the water, no chemicals are used and there’s no waiting for the chlorine to evaporate.

They can be used for complete pond fills or for just topping up.

We found a couple from, the Evolution Aqua Detox Dechlorinator 12 inch also available in 30 inch and the Oasis In-Line Dechlorinator.

This is the most expensive way to remove chlorine from tap water, but it’s quick and you’re not adding chemicals into the pond which makes it a good choice.