Do you have the right water in the aquarium?


Water is water – or is it?

Water varies in a number of ways all around the world

  • Some of it is suitable for human use without treatment or change
  • Some waters have iron, or sodium, or lime in such quantities as to be unpleasant to drink, at least to the uninitiated.
  • Mineral compounds of calcium or magnesium are called “hardness” compounds and waters throughout the United States and Canada range from completely soft (or without hardness) to extremely hard.

What water options do you have for your aquarium?

  • Tap water
  • Reverse Osmosis (RO) and De-ionized (DI) Water
  • Distilled water
  • Spring Water and Bottled Water Sources

Tap Water

Tap water is accessible everywhere.

It is sourced either from a municipal water sources or from a well.


Factors to consider when you choose tap water

  • It’s easy to source
  • Municipal water sources normally contain chlorine or chloramine to kill bacteria
  • Well water sources may contain phosphates or other organics
  • Tap water can be used, but should be treated or purified to remove these materials before it goes into your aquarium.

Reverse Osmosis (RO) and De-ionized (DI) Water

Reverse Osmosis and De-ionization are often done in conjunction with and in combination with filtration systems.

Water is forced through a membrane (RO) and through resins (DI) that remove minerals and compounds leaving the water very pure.


Factors to consider when you choose RO/DI

  • Filtering tap water does not remove chlorine and chloramine compounds used in tap water purification. You will need a carbon prefilter
  • RO/DI filtration removes most compounds including some necessary ones. That means RO/DI water must be buffered and remineralized before being used

Distilled Water

Distilled water is very pure because it is collected from pure steam.


Reasons why distilled water is rarely considered for aquariums

  • It is very expensive
  • It is inefficient when it comes to tank maintenance
  • It is very pure and has had even more minerals and compounds removed than other processes
  • It is extremely soft and has no buffering capacity or mineral composition
  • You will have to replace mineral by mixing salt mixes for reef systems but it would need to be buffered before it can be used for freshwater
  • Without being buffered, distilled water chemistry parameters like pH can fluctuate wildly. This makes distilled water unsafe
HOW TO: Make Tap Water Safe for Fish

How to group fish according to water types

It’s very tempting to put a few fish of several varieties in the same aquarium because you want to add more life and color to the aquarium.

Unfortunately different fish require different types of water.

Grouping fish according to water types

You should combine a few fish of several varieties in the same aquarium

  • If they are all hard-water or all soft-water fishes
  • If the can get along well together

The first requirement for a successful and thriving aquarium is water

  • Have your water tested in a laboratory, or test it yourself for accurate hardness and pH
  • If you have using copper water piping, have your water tested. Copper is poisonous to most fish, and enough may be present in the water to harm them.
If the water is too hard

Soften the water using softeners designed for aquariums. This can be done after the water is in the tank.

If the water is too acidic

If water is either too acid, it should be corrected very slowly to avoid over-correcting.

  • Add one half teaspoon of bicarbonate of soda (baking soda) at a time to ten gallons
  • Recheck the pH after 24 hours, and add another one-half teaspoon if needed
  • Continuing this process until the desired pH is reached
If the water is too alkaline
  • Remove some of the water and replace it with water that is more nearly neutral
  • For spawn­ing, put peat moss directly in the tank
  • Boil a handful of peat moss can be boiled in an enamel pan and add the resulting tea progressively to get the desired pH

Filling the aquarium with water

Now that you have some knowledge of the water that is to go in your aquarium, it is time to fill it.

How to fill the aquarium with water

  • First put a saucer on the sand in the aquarium, or cover the sand and rocks with a sheet of brown paper held down by pebbles.
  • If a tap is to be used, a piece of hose can be fitted on it and a slow stream of water brought to the aquarium and directed onto the saucer or paper.
    • This should allow the tank to be filled without disturbing the sand
    • The water should be quite clear at the end of the operation.
  • If a hose cannot be used, a pitcher can be used to pour in the water. When the tank is full, the saucer or paper can be gently removed. Do not worry if there should be a slight clouding or mistiness, as this will soon settle down.
    • The inside of the glass, and probably the surface of the rocks, will now be covered with millions of glittering little bubbles.
  • Next, put the heater, if any, in its place in the sand, taking the wire up one corner of the tank where it will show the least. Connect it to the thermostat, and the thermostat to the main supply, and switch on. As the temperature rises the bubbles of air will gradually go to the surface and disappear.
  • Should any of the sand have floated to the top, as it does occasionally, touch it with the finger and it will fall to the bottom.
Aquarium Set Up – Beginning to fill the new fish tank

Points to remember about water in the aquarium

  • Some water should always remain in the tank indefinitely
  • The water does not have to be changed every day or every month
  • There will be a slight loss due to evaporation, which will have to be made up every now and then by the addition of a little freshwater
  • Siphon off a third to a half of the water once each month, replacing it with freshwater. This will keep the hardness under control if you do not use a softener.
  • When the tank is full it should not be moved to avoid straining the angle bars of the aquarium and start leaks
  • If you need to move the tank, take out the greater part of the water before doing so