Once upon a time, people believed that heating distilled water was dangerous because it heated faster then regular tap water. This has since been proved to be untrue. Distilled water does not heat any faster then your everyday, run of the mill, tap water.
The definition of distilled water is water that virtually has had all its impurities removed through the act of desolation. Water is distilled by boiling it. As the water boils the steam is captured and then re-condensed into a clean container. Many companies have started considering cheaper alternatives for purifying water, one such method is deionizing the water. As of yet alternate methods, while successful, have been unable to completely purify the water.
Distilled water is commonly used in lead acid batteries, automotive cooling systems, and steam irons.
Another popular use of distilled water is in aquariums. Aquarium enthusiast use distilled water in their tanks because it lacks chemicals that are often found in run of the mill tap water. Many tap waters contain chlorine and chloramine, which are fatal to fish.
All to often aquarium owners are stunned to learn how much money they spend each year just by purchasing gallon after gallon of distilled water. On way saltwater aquarium owners can save money is by distilling their own water, provided that they are willing to improvise. The first thing you will need to do is to find away to heat/boil the water, this can be done with either a gas or electric stove. Any normal cooking pot will do for the heating. The next thing to do is find a way to catch and cool the steam, because the typical cooler is made out of a long spiral shaped piece of copper tubing. Saltwater aquarium owners will have to find a different piece of tubing because water distilled in copper is fatal to the invertebrates that live in coral reef. If you are unable to find a spiraled pipe consider using a pot and to lids. As the water boils it will start to condense on the lid of the pot, this is distilled water. Cover the pot with the second lid and pour the condensed water into a cup. Repeat the process until you have enough water for your tank. It takes a long time to gather enough water.
When setting up a saltwater aquarium it is important to remember that the distilled water must be supplemented. By itself the distilled water is to pure to sustain aquatic life. It is also important to make sure that the distilled water you are using has not been stored in any containers containing copper. The addition of copper in the saltwater is lethal to the invertebrates that live in coral reefs.
Anyone who is unsure about the purity of their tap water should plan on using distilled water when they are setting up a saltwater aquarium. Make sure you add a saltwater mix to the distilled water.
After filling the tank with water and installing your filtration system it's recommended that you let your tank sit empty for a few days. When the water quality tests accurately after the tank has been running then you can add your fish. Double checking your water could potentially save you from accidentally destroying your fish.