Adding salt to freshwater

Question
Hi! I hope this isn't considered a saltwater question. I have a 55 gal. hexagonal tank I just set up about one month ago and another 30 gal. that has been set up for two years.
  In the 55 gal. I have two lima shovelnose cats (about 9" long) and a albino clown knife (about 7" long). I have 5 tiger oscars in the 30 gal. right now. I know that this is too many oscars for that tank but I wanted to weed out the weak ones and throw the two strongest oscars in the 55 gal., eventually returning one or two oscars after they outgrow the 30 gal., and the clown knife or one catfish (whichever one I am least attched to)from the 55 gal.
  My question is whether the cats and clown knife can tolerate aquarium salt. I know that some salt is recommended with oscars but I can't find much information looking online using keywords of "salt" and "catfish" other than recipes. My fish aren't big enough to eat yet. Just kidding.
 Another question I have is how long it takes an oscar to become accustom to a new enviroment. I did throw two of the larger oscars into the new tank and they seemed pretty stressed. I took them out after 3 days cause I was worried about them. Now, after only 3 hours they are back to themselves and are as active as ever. Have you ever heard of oscars getting "lonely" and becoming attached to there school. Well any help would be awesome.

Thanks, Luke.

Answer
Hi Luke,
 I disagree about salt being recommended for oscars.  I would never put salt in an oscar tank. Oscars come from the central Amazon and there is absolutely no salt in their natural water (I've been there).  

 Yes, oscars get very used to their home environment, moreso than any other fish I know of.  In fact, they even get very attached to people.  I get a lot of questions from people who say that suddenly the family oscar is mopping around the tank, and often it turns out that a teenager has moved out to college or something like that.  Oscars can take a long time (weeks or even longer) to get accustomed to a new place and new faces.

P.S. You are aware that an adult shovelnose cat is close to 3 feet long or more, right?

-- Ron
  rcoleman@cichlidresearch.com
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