Agree with above, happened to my tank.
BTW murky has a U not an E
I'm that picky
is your gravel clean
clean the inside of your filter if its old
did you set it up today
if so just leave it for a few days really it will be crystal clear soon enough leave the filter running and the heater on
was it brand new or second hand ?
and when you cleaned the gravel was the water clear after washing the gravel
  i noticed the filter had little pellet type things in it under to spongey bit am i suposed to leave them in? i did! 
ermm yes leave them in the filter in fact i havnt got a clue what they could be as i dont really no much about the biorb filter system but im guessing that its part of the media i.e carbon or sumthing like that but honestly just leave ya tank and i will clear just out of interest now whaty you going to be putting in the tank (fish wise)
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do you have a api liquid tester kit if not get 1 to do you water checks
