Water Evaporation

Question
Hi i have a saltwater tank and when the water evaporates i
don't know if its a good idea to add  boiled tap water or with
what type of water should i refill it with for the salinity to
be where its suppose to be?  

Answer
Hi Oscar,

Saltwater aquariums should be topped off with reverse osmosis filtered freshwater or deionized filtered freshwater, or a combination of both reverse osmosis / deionized filtered freshwater. Typically, you will see the abbreviation RO or RO/DI used for this type of water.

The reason you only need to top off your aquarium with filtered freshwater versus saltwater is because the salt does not evaporate, only the water evaporates, leaving the salt in the tank.

You can find this water at your local fish store or purchase an adequate filter and make the water at home yourself.

Alternately filtered water can be purchased from some grocery stores, however this is typically more expensive, and you would have to make sure no additives such as flavoring or other minerals have been added to the water. See the link below for information on a RO/DI filter unit, that you can install at home to make top off water.

http://www.ocreef.com/aquafx_octopus_rodi_system

Regards,
Dave