cloudy tank... Oscar scales patchy and white

Question
I have two Oscars (about in long each), 2 gouramis (about 4 in long each), 2 placos/algae eaters (6 in long each) and a Raphael Catfish (about 3in long) all in a 55 gallon freshwater tank. They have all been in the tank together for about three months with no problems. Recently the tank has become cloudy and the Oscars had patchy white scales that resemble scars. I have changed the water, added pH balancing chemicals, ammonia and chlorine neutralizers, and vacuumed the tank (not all at the same time). Each time I try one of these methods the water clears and the patchy scales disappear for about two weeks before the cloudy/patchy cycles seems to begin again.

Also one of the two Oscars has been moving rocks. The Oscars seem to be the only ones affected by the cloudy water. What do you think is going? and what else should I try?  

Answer
Hi Bobby,
 I think something got messed up in your message because it says that your oscars are an inch long.  I suspect that they are longer, particularly if one of them has started moving gravel.

  A tank becomes cloudy because of a bloom of bacteria. That happens when there are too many nutrients in the water.  That is usually the result of infrequent water changes and/or overfeeding.  You should be changing 25% of the water once a week, every week, to keep your tank happy and healthy.  Only feed what the fish eat right away.  Never put in food for them to "eat later". It will rot and cause the tank to go cloudy.

-- Ron C.
   rcoleman@cichlidresearch.com
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