I am in the process of buying Tumbled Marble mosaic tiles online and have asked the retailer if they will need sealing.He has told me they will need sealing after laying and then after grouting.Now my question these tiles are for a bathroom walk in shower,what is the best adhesive to use and what is the best sealer to use and also grout.All help would be greatly recieved as im not exactly a professional(diy trier)