Cloudy tank for months

Question
Hi.  I set-up my tank 2 months ago.  I have had some challenges with brown algae, way off pH, ammonia, nitrite and nitrate balances and so on.  Recently my three sifting sea stars died.  It wasn't a surprise.  However, now all else  seems to be going well.  Every level (except Ammonia at 0.75) has been kept at bay.  My volitan lion and puffer have been very active.  My yellow tang has these "dark lines" outlining his eyes and some other parts of his body which concerns me.  But here is my problem, since day one, my tank has been cloudy.  I thought it was the sand so I waited.  Then I got one bag of bacteria (150 gallon tank) and it didn't do much.  How do I get my water to clear up?  Thanks in advance.

Answer
IT KIND OF SURPRISES ME THE LION AND PUFFER ARE DOING SO WELL, HOWEVER THEY ARE HARDY SPECIES. THE TANG DOES NOT SOUND LIKE HE'S DOING WELL.TWO MONTHS IS NOT A VERY LONG TIME TO BE SET UP. SOMETIMES, IT TAKES THAT LONG FOR THE TANK TO CYCLE. WHAT ARE YOU USING FOR A FILTER SYSTEM? DO YOU HAVE A PROTEIN SKIMMER? THE BACTERIA YOU ADDED - WAS IT A BARLEY FLAKE TYPE? IS YOUR TANG EATING? ALSO GO TO ABOUT.COM AND CLICK ON HOBBIES AND GAMES, THEN CLICK ON SALTWATER AQUARIUMS AND YOU WILL BE AT THE SITE RUN BY STAN AND DEBBIE HAUTER. YOU WILL BE ABLE TO FIND ALMOST ANY ANSWER TO ANY QUESTION, BUT PLEASE GET BACK TO ME WITH SOME ANSWERS AND I WILL TRY TO HELP. GERRY.