Traumatized fish after death of one of their mates

Question
Before I went on vacation I set up my fish tank with an automatic feeder as well as a solid dispenser in the tank.  When I returned home one week later one of the fish had died and was floating on top of the tank.  It appeared that the fish must have died almost immediately after I left since it was in a wretched state of decay.  

I realize you do not prefer to answer questions about goldfish but felt this behavioral inquiry may be of interest to you.  Since the death of the fish, the other two fish in the tank have been huddled in a corner behind a decorative statue.  They only come out to eat.  I have replaced about 75% of the water since it was quite oily and had a horrible odor from the incident. Are they going to be okay?  How long will they behave this way?

Answer
Hi Rebecca,
  It is not that they are traumatized because they "miss their friend". The problem is that fishes of that group, namely the minnows and relatives, release a particular substance, called "shrekstoff" which literally means "fright substance" when they die.  Other minnows can detect this stuff and get frightened.  It is in essence a warning sign for other fish.  

  Bottom line: you need to do a lot more water changes.  Change 50% of the water everyday for about 4 days and I suspect that the remaining fish will perk up.

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