Purify tap water
Everyday tap water is dangerous to fish. Tap water includes chemicals that make it safe to drink for humans, but damaging to aquarium inhabitants. Chlorine, chloramine, copper, nitrate, and other heavy metals found in typical drinking water must be removed before adding it to your aquarium.
In a freshwater aquarium, removing the chemicals can be as easy as adding a commercial “Tap water conditioner” found at most pet stores. These conditioners must be added to the water before exposing the fish to the water. There are many available brands on the market. Usually, once added, they work instantly to detoxify chlorine and heavy metals that are within the water.
However, in a salt-water set-up, where the fish can be much more sensitive to the effects of these chemicals, it is best to purchase a reverse osmosis/deionization system to purify the water. The system, referred to as RO/DI, consists of a reverse osmosis membrane through which the water flows (and is purified), followed by a deionizing resin that removes any residual charged compounds. Typically, other parts of the system ensure that these two main parts function properly. These other parts may include sediment filters, activated carbon filters, pressure gauges and conductivity or total dissolved solids monitors.
As with anything in the aquarium world, doing extensive research will go a long way in making sure your fish live a long, healthy life. This will help prevent you from making mistakes that could potentially harm or even kill your fish. It will also save you time and money in the long run.