Multitude of fish issues

Question
I have had aquariums since I was a little kid and have seen fish die and fish live ..........and then die eventually (natural causes I assume for a fish in captivity, disease or not it was there time)
  I recently resealed a 55 gal that I recieved frommy grandparents. It was the aquarium that first got me into fish about 15 years ago.
  This started out as a bad experience using the incorrect silicone (anti-biocidal agent). That has past. I scraped and scrubbed the tank for 4 days to rid myself of all of the bad silicone and resealed it with some aquarium sealant I ordered from a pet store. I ran the tank for 48 hours and had a problem with cloudiness. I, from my experience, knew that this was bacterial bloom. I corrected it by throwing in the filter from my 30 gallon tank to get some bacterium growing and got results in only 2 days. The water is still a little cloudy only noticable in direct sunlight making it 95 % better than it was.
 I transferred the fish that had made it from the original ordeal ( a clown knife, two lima catfish, and of couse a pleco) and two tiger oscars I recently bought for the tank. My issue is with the oscars. They are acting strange and are hanging at only the bottom of the tank behind some foliage. The funny thing is that they were recently this morning being very active. I was wondering if this was normal for oscars.I also had a curiosity if adding salt was all right for all of the fish in question. I have heard about adding salt to improve the oxygen transfer of my fishes gills, but also have heard that salt is untolerable by other aquarium species.  Also, I have only heard of salting water if fish are sick. If salt does help I would like to add a small amount but if any of my fish cannot handle it I will not add it. The think is is I cannot find if any of my fish, other than the oscars can handle salt. Well thanks for your help, Luke

Answer
Lucas hi,
Your fish tank should improve but I would have done was bought starter fish for a brand new tank so that yor not to attatched to the fish if they die.It is alright to add salt even with all of those variety of fish though. You shuold add about a tablespoon per each ten gallons,
 Hope I awnsered some pondering questions,
                                 Samantha

P.S- I dont recall oscar fish acting like this but if they have a disease you can find out at this website
http://www.tropicalfishcentre.co.uk/Diseases1.htm