You didn’t say whether your mosaic is natural stone, stone and glass, just glass, ceramic or porcelain. Regardless, you may want to grout your tiles to fill in the cracks between them. Use un-sanded grout.
o STONE: Make sure that you keep it properly sealed and wipe off splatters as soon as they appear to avoid stain setting. Just use warm water and a mild detergent daily over the area and a proper natural stone cleaner about once a week. Use nothing acidic like vinegar and water nor use those advertised household cleaners as they will etch your stone. You should use a proper stone cleaner once a week or so. We, at Interstone Marble and Granite endorse FILA brand products.
o GLASS, CERAMIC, OR PORCELAIN: With these materials, you can basically use any household product you wish to clean your countertop. Glass cleaner, foaming cleanser, or warm water and a mild detergent you would use on your hands. There’s no inherent need to seal these materials either.