First of all lets dispel a myth about the best water for your Betta fish. You do not use bottle water. It seems as though some people think that just because you have a unique tropical fish that you have to go out and get bottle water to create the possible environment for them by buying the most expensive bottle water on the market.
Bottle water maybe one of the most harmful environment for your Betta fish. Bottle water may contain some harmful chemicals to your Betta fish. Bottle water also do not contain the essential minerals Betta fish need to survive. Also distilled water and purified water should never be use even if you use a filter because it will not contain the minerals needed for your Betta fish.
This may come as a surprise to many people but plain old tap water is all you need for your Betta fish. If you have been using bottle water you need to switch back to tap water right away. The switch will not harm your fish no matter how long you have been using tap water.
If you have to use bottle water it should be spring water and the following steps below should be followed to get the chemicals out of the water. Most of our drinking water contains chemicals also but the steps below should easily take care of the problem.
Since most local water is treated with chemicals you need to find out if it has been treated with a chemical named chloramines. There is special treatment for the chemical chloramines called AmQuel. You can usually find AmQuel readily available in most of your pet stores.
You must also treat local tap water because plain tap water will kill your fish. Tap water should be treated with a product named “stress coat” which also readily available in your local pet store.
Be sure to follow all the directions according to package because after treatment there is an ageing process that must take place. The directions on the packages will advise you how long that process should be. The ageing process allows all the chemicals and gases to evaporate. Most directions say after treatment of the water let it sit in an open container for about a week.