Silver Dollar Behavior

Question
I have a newly set up 55 gal aquarium.  After the water cycled we put in two Silver Dollars, two Bala Sharks, two Rosy Barbs and two crabs.  All fish are doing quite well and water quality checks all turn out normal with the exception of moderately hard water.  The problem is that after feeding one of the Silver Dollars starts swimming side ways, upside down, and has a very hard time keeping from floating to the top right after feeding Tropical Fish Flakes.  He will float around the tank and try his hardest to stay off the top.  He started this with last nights feeding and returned to normal within about 10 minutes.  After this mornings feeding he floated to the top several times and just floated there and I thought he had died.  I tried to go after him with the net and then he would take off, swim irratically for awhile, and then float to the top again.  This behavior lasts about 15 minutes after putting the food in the tank.  Again, after about 10 minutes he's fine.  The other Silver Dollar isn't showing any signs of this at all.  Is it something in the food?

Answer
Hi Barbara,
 I really doubt that it is something in the food.  More likely it is a problem that is just exacerbated by the fish trying to feed.  Sadly, when fish start displaying that sort of behaviour, they seldom recover.  I don't know exactly what causes it, i.e., whether it is neurological or intestinal. Sorry.

-- Ron
  rcoleman@cichlidresearch.com
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