Using natural seawater from the ocean for your reef tank can be a viable option, but it is important to consider the potential risks and challenges involved.
One potential risk is that seawater may contain harmful substances or pollutants that can be harmful to your tank's inhabitants. Additionally, the salinity and chemical composition of natural seawater can vary significantly depending on the location and time of year, which can make it difficult to maintain consistent and stable water conditions in your tank.
To minimize these risks, it is recommended that you only use seawater from a reputable source, such as a local fish store or a specialized supplier that has tested the water for quality and safety. You may also want to consider using a reverse osmosis (RO) or deionization (DI) filtration system to further purify the water before using it in your tank.
Alternatively, many reef hobbyists choose to use artificial salt mixes to create their own synthetic seawater. This allows for greater control over the water conditions and can help to ensure a consistent and stable environment for your tank's inhabitants.
Ultimately, the decision to use natural seawater or synthetic saltwater will depend on your personal preferences and the specific needs of your tank and its inhabitants. It is always recommended to do your research and consult with experienced aquarists or professionals before making any major changes to your aquarium setup.