hello and welcome m8
yes this is normal as water isnt absolutly clean from your tap and if you have plants logs bricks gravel the dirt from these will mix up in the water when adding it
do you have a filter running ? also if so this will clean your water fast depending on what filter you have of course the more you spend the better meaning faster better
if you have standard filter i say within day 2 most it should be clean
But you say you cleand the gravel you really dont want to do this
by cleaning the gravel your mixing dirt back into the water =it will need to reestablish itself
another thing is you Shouldnt clean your gravel becuase this is where the important bacteria needed to remove fish waste lives and you cleaning it will remove it
how long has it been up /with water /you dont have fish do you ?
also you need to cycle your tank (New tank syndrome )
this is the word given to a tank going thru its nitro cycle and building up helpfull bacteria needed to brake down waste this can take a max of 6 months but most normal is 3 months if well done
there are 2 ways to cycle your tank WITH or WITHOUT fish /using hardy fish i.e zebra danios barbs and couple of others that are well known for being used while you cycle as they can take much more then most fish
1st you must understand about cycling your tank befor help can really be given
to be a world number 1 rally driver 1st you must be able to drive you get me ?
check out the link for more info
what is new tank syndrome