Can you use tap water for a fish tank?

can you use tap water for an aquarium header

In the eyes of the outliers, the aquarium hobby seems quite simple.

Unlike experienced aquarists who play it safe, they think you can just take fish, use tap water to fill your aquarium, and put it straight in.

The reality is that sink water needs to be conditioned before it can be used in an aquarium because it contains a bunch of chemicals. There are also different types of water that can be used as an alternative, but before we get to that, let’s answer the question first.

Can tap water be used for an aquarium?

Of all the different sources of water one can use for an aquarium, tap water seems to be the most convenient.

However, is using tap water really such a good idea, or is there something fishy about it?

Here’s if you can use tap water for your aquarium:

Water treatment facilities use chlorine and chloramine to disinfect tap water from pathogenic bacteria. These substances also kill the good bacteria in an aquarium and disrupt its nitrogen cycle. For this reason, tap water can only be used for pet fish if it is first dechlorinated.

In addition, chlorine and chloramine have a direct impact not only on colonies of beneficial bacteria, but also on fish. When fish are exposed to chlorine, the substance enters their bloodstream and begins to destroy their cells.

This results in burns all over their body which could then affect their gills and kill them. Even if they survive the initial shock, they would be very stressed and would not live long.

Related: Why do fish die or get stressed after a water change?

I think I’ve given you enough reasons why using water straight from the tap is a bad idea, so let’s take a look at the different ways to dechlorinate it and add it to your tank.

How do you dechlorinate tap water to make it safe for fish?

1. Use a water conditioner

seachem prime water conditioner

by Bwood22

The most popular and easiest way to dechlorinate water is to use a water conditioner such as Seachem Prime. All you have to do is add the recommended amount of conditioner to the water and let it do its magic for about a minute.

I try to recommend Prime to beginners in this hobby because it’s easy to use and can save them a ton of headaches. I also use it myself because I think it’s unrealistic to keep a piece of the ocean at home without the help of some cleverly designed chemicals.

However, some people dislike the distinct sulfuric smell of water conditioners and prefer to dechlorinate their aquarium water naturally.

If you also want to make your tap water safe, without using conditioners or chemicals, you can try one of the following methods.

2. Let the water stand

leftover tap water

Designed by edgardcafe

Many sources online recommend letting your water sit for 24 hours as a means of purification.

While their claims have some merit, they fail to acknowledge the many factors that affect chlorine evaporation times.

Evaporation times for chlorine and chloramine are closely related to UV exposure, circulation and ventilation.

Also, some water fixtures may use larger amounts of chlorine or even chloramine instead, so following the “24 hour” rule alone will get you nowhere.

I’ll use an example to show you how combining some of these factors to your advantage can have a huge impact on evaporation times. If you let 10 gallons of water sit in a dark room with some ventilation, it can take you up to 55 hours to completely dechlorinate 1 ppm (parts per million) of chlorine.

However, this time could be reduced considerably, if the water is in circulation and is exposed to ultraviolet light. Ultraviolet light forces chloramine and chlorine out of the water at a much faster rate, while the movement of the water speeds up the process by bringing it into contact with the air.

To achieve these same effects, simply put the water in a glass container with a filter or wave generator and let it flow for as long as necessary. Visit the link to see some data I collected on how long it takes for chlorine and chloramine to evaporate from tap water.

3. Campden tablets

potassium metabisulphite

by Citizensnips

Campden tablets (sodium or potassium metabisulphite) are a key ingredient in the brewing of beer, wine and cider.

They are used for water sterilization because they kill bacteria and inhibit yeast growth.

How is that compared to fish farming?

Well, as an added benefit, these tablets also purify water by removing free chlorine and chloramine.

They work much the same as typical water conditioners, but take a little longer.

Unlike conditioners which work almost instantly, Campden tablets need about 20 minutes to take effect.

The downside to this method is that these tablets are hard to find unless you live near a specialty brew shop, in which case I would really envy you.

4. Boil and wait for it to cool

boiling water

by SaltNeck

Boiling can be a relatively quick way to purify your water, depending on whether it’s chlorine or chloramine. One ppm of chlorine dissipates from boiling water in less than four minutes, but it would take over an hour for the same to happen if your water is disinfected with chloramine.

This is because the chemical structure of chloramine contains an ammonia bond, which is not present in chlorine.

This extra binding makes it much more stable at higher temperatures and is also the cause of the ammonia spikes after dechlorinating the water with a commercial water conditioner.

Due to these large differences, it is advisable to contact your local authorities and check which compound they use for disinfection.

Otherwise, your attempts to boil off the chemicals would be nothing more than a shot in the dark.

5. Filter by reverse osmosis

reverse osmosis system

Designed by EucalyptusHelve

Osmosis is a physical process in which solvents move through a semi-permeable membrane from areas of high water potential to areas of low water potential.

In reverse osmosis, there is an external pressure which overcomes the osmotic pressure and moves the solvent in the opposite direction, forcing the solvent to the pressure side of the membrane.

This purifies the water leaving the overly large particles trapped on the other side of the membrane.

Reverse osmosis systems remove 90-99% of impurities from water, but they also filter out minerals. Without any minerals in the water, the osmoregulation of fish is disturbed, which ultimately leads to their demise.

This is because osmoregulation is the process that controls water retention in fish and their absorption of minerals from their environment.

In short, if you use this method, you will need to remineralize the purified water before adding it to your tank.

To purify your tap water using reverse osmosis, you would need a specialized reverse osmosis and deionization unit. Although not cheap, these systems are excellent for reducing phosphate levels and minimizing the risk of algae growth.

6. Use Vitamin C

vitamin C

by noscrub_mp3

It turns out that vitamin C has many more practical applications than just fighting colds, and one of them is cleaning large amounts of water of chlorine and chloramine. In fact, the US government recommends it for neutralizing chlorine in water systems because it is safe for marine and aquatic life.

To prepare your aquarium water using this method, you need to add 2.5 parts ascorbic acid to 1 part chlorine.

It will take about five minutes for vitamin C to work and purify tap water of any chlorine.

For chloramine, however, you would need about 40 mg of ascorbic acid per gallon of water to achieve the same result.

Keep in mind that vitamin C can lower the pH of your water, so it’s a good idea to test your water parameters for any changes after dechlorinating it this way.

What other types of water can you use instead?

add water to the tank

by Kogre

Besides tap water, there are several other types of water you can put in your tank.

Each of them, however, has its own advantages and disadvantages. Let’s see how they compare:

Distilled water

Distilled water is water that has been recovered after being turned into steam. This destroys bacteria and purifies the water of chlorine and other harmful substances.

Purified drinking water can be purchased at any grocery store and is not that expensive. Unfortunately, you can never be sure that the brand of water you are buying was distilled using copper pipes. Studies have shown that exposure to copper has adverse effects on the health of fish, so it is best to avoid using commercially available distilled water.

Also, to be safe for fish, distilled water must be remineralized because it is stripped of its minerals during distillation.

Bottled water

Another possible option, although less convenient for your reservoir, is bottled mineral water. Bottled mineral water typically contains more than 250 ppm TDS of trace elements. Its mineral content makes it an excellent choice for freshwater aquariums with fish that thrive in hard water.

This saves you a lot of unnecessary tinkering with water parameters that you would otherwise have to do.

Or at least you would think so.

Bottled water mineral measurements can sometimes be unreliable, and there is also no guarantee that the water has been treated with chlorine or chloramine.

Bottled mineral water is also more expensive than regular tap water, so it might not be the best option if you’re on a budget.

spring water

Spring water is any type of water that comes from an underground spring around the ground or rock beds.

The mineral content and pH of spring water vary greatly depending on the aquifer or source from which the water originates.

For this reason, I wouldn’t recommend using spring water unless you have an established brand you can trust.

Also, carrying 50 gallons of water from the store isn’t the most practical thing you can do.

Last takeaway

To provide a suitable environment for our fish, we have to overcome many obstacles and the dechlorination of tap water is just one example.

However, even if they have no way of showing it, our pets surely appreciate all our efforts.

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