Home Fish Facts Can Fish Live In Tap Water? (Important Facts)

Can Fish Live In Tap Water? (Important Facts)

by gvald

In order for tap water to be drinkable for humans, it had to undergo several treatments. The use of chlorine has allowed eliminating bacteria and other …

Although tap water is good for us, it is not good for your fish, but it is possible to condition it to suit your aquarium.


By using a suitable conditioner, your tap water will become healthy and suitable for tropical fish like guppy, neon, botia clown, harlequin fish …

For cold water fishes, same treatment, you have to use a conditioner. This will transform tap water into biologically appropriate water for your goldfish and other cold water fish.


Why shouldn’t you use tap water in the aquarium?

Tap water is fortunately very clean in most countries nowadays, so for us humans it is the most suitable drinking water. However, there is still a crucial difference between drinking water that is safe for humans and water that the aquarium inhabitants feel comfortable in.


Occasional treatments with chlorine and low concentrations of heavy metals are not uncommon, even according to modern safety standards. Harmful substances introduced into the aquarium from the tap water, such as chlorine and heavy metals like copper, lead or zinc, often damage the gills and skin of the fish first.


In addition, these harmful substances can also damage the bacteria responsible for the nitrification process, so that the biological filtration does not work perfectly and the ammonium and nitrite values increase.


How to adapt tap water for fish?

To prevent these risks, water conditioners can be used. These condition the water immediately and reliably into a water suitable for fish, removing harmful substances such as chlorine and chloramine, binding heavy metals and preventing ammonia concentration. This does not affect the water values even with multiple doses.


In a new installation, a conditioner helps to quickly create a safe environment for beneficial filter bacteria. In combination with filter pellets, which contain porous volcanic rock and millions of filter bacteria, the new population can be introduced in only 24 hours.


How long does a fish survive in untreated tap water?

Yes, water is the living environment of fish. It feeds, breathes and reproduces in it. It also discharges its waste into the water.


However, water that seems dirty to you is not always unhealthy for fish. Indeed, when water is clear, like tap water, there is no life or food in it. The fish can’t live in it for long, maximum a few hours. Because without bacteria to eliminate excrement and food residues, the waste quickly poisons the water.


Which water to use for your aquarium?

For a freshwater aquarium, it is possible to use tap water, provided that it is conditioned. But is it the best? Wouldn’t it be better to use bottled water, rainwater, osmosis water or mineralized water?


Osmosis water

Among aquarists, osmosis water is considered the best water for an aquarium:

It is the result of a very powerful filtering process for a pure result of 95 to 99%.

Osmosis water is therefore softened and free of all harmful elements: nitrates, heavy metals, pesticides, limescale, etc.


Rainwater for aquariums

More economical and purer? Not so sure: in theory, rainwater is pure because it is not filtered by the soil. But in reality, as it falls, a drop of water is loaded with particles and dirt.


You can therefore collect it, but you will then have to :

filter it ;

  • Adjust its pressure with a compressor (small water pump);
  • Add the necessary nitrates for your fish.


To summarize, rainwater requires relatively important equipment to obtain water compatible with your aquarium. It’s up to you if you want to take on this project.


Filling the aquarium with bottled water

Why not fill your aquarium with bottled water? While this may be better for your fish, you also won’t have to make any special trips to get supplies!


  • Although it is indeed possible to fill your aquarium with bottled water, you should not use just any water.
  • Above all, select :
    • Spring water with low “ion” content (calcium and magnesium);
    • Water with the lowest pH: the lower the pH, the less charged the water.


You can choose specific waters to cut your tap water to balance the contributions. Moreover, from an economic point of view, we advise you to couple bottled water with packaged tap water.

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