Wierd behavior, Oscar fish

Question
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Followup To
Question -
Usually my Oscar is very calm and friendly, as of last night I think he may have gone crazy! Normally I can touch the outside of the tank and he goes right up to my finger and almost "plays" with me. Last night he started acting very scared when I would approach the tank, if I didnt have a cover on the tank he may have jumped out because he really freaks out and all of the water splashes when I touch the tank. Also whenever I approach he moves way to the back of the tank almost in fear. He is also a little tilted. I cleaned my tank yesterday, removed about 40% of the water and added only Aqua Safe and tank salt. Can you help me? Also the water doesnt smell, there is no irregular temperature water and he is well fed. Thanks!!!!!
Answer -
Hi Sophina,
  It isn't generally a good idea to replace so much water at once.  I try to stick to 25% at most.  It is far better to change 25% every week than say 40% every two or three weeks. The change in water chemistry can cause fish to "freak out" sometimes so that could be the problem.
 I see no value in adding salt to an oscar tank.  

 I don't think there is anything that you can or should do in the short term, i.e. I wouldn't add any more chemicals to the tank. Let me know if anything changes.  

 He/she isn't nesting by any chance, i.e., moving a lot of gravel and creating a big pit?

-- Ron
  rcoleman@cichlidresearch.com  
  Cichlid Research Home Page <http://cichlidresearch.com>

Thank you so much for getting back to me so soon! In response to your question, no he is not nesting or moving a lot of gravel, nothing like that at all. But just in case he does, what does that sort of behavior mean? I won't add anymore chemicals to the tank, under the advice of an aquatic "expert" I added the tank salt, he said it was good for the fish and adds electrolytes to the water. Another thing, I usually remove that much water when I clean the tank, but I will follow your advice and only remove 25% of the water from now on. But thank you so much again.  

Answer
Hi Sophina,
   If he was nesting, e.g., clearing the gravel away from part of the tank, he could get quite defensive about it and that is why he would act "crazy".  

  Salt is an interesting issue.  The idea of adding salt to cichlid tanks dates many years back when there was this notion that cichlids were "secondary" fishes, meaning that they derived from marine fishes that returned to freshwater over evolutionary time.  We now know this idea not to be true yet the idea that they should have some salt persists.  
I have been fortunate enough to actually snorkel in the Amazon, where oscars come from, and there is no salt in the water at all, quite the opposite.  There is very little of anything in the water.

  Some people still insist on adding salt saying that it is good for the fish, but all my academic training (I teach ichthyology -- the study of fishes -- at Cal. State University Sacramento) tells me that salt should have the opposite effect: in theory, it should stress a fish like an oscar because now the fish has to deal with adjusting its internal salt balance against something that it hasn't evolved to deal with, namely salty water.  One of the arguments for adding salt is that freshwater parasites have an even harder time making this adjustment, so they die, but it only hurts the oscar a little.  I'm not too thrilled about that idea so I never add salt to my New World cichlid tanks.


-- Ron
  rcoleman@cichlidresearch.com
  Cichlid Research Home Page <http://cichlidresearch.com>