* Mechanical mixtures are combinations of substances where each component retains its own properties and can be easily separated. Think of sand and water, where you can see the individual grains of sand and easily filter them out.
* Water in a fish tank is a homogeneous mixture, also known as a solution. This means that the components (water, salt, minerals, etc.) are evenly distributed and cannot be easily separated by physical means.
Think about it:
* You can't see individual particles of salt or minerals in the water.
* If you try to filter the water, you might remove some impurities, but you won't be able to separate the salt or minerals completely.
In summary: While the water in a fish tank might have several components, these components are dissolved in the water and form a solution, not a mechanical mixture.