dont worry its normal they will go in there own time around a few days or so
your sand and rocks will next start to change and get browny red algea on this is the cycle the marine tank takes it could last a few weeks or months
do not rush adding fish etc take your time nothing should be added for a few weeks / month or more may be just a few clean up crew craps snails ect if l can help you any more please just ask
injoy your tank :mrgreen: