Zebra Danio has a lump

Question
QUESTION: Hi Ron,
My Zebra Danio has a small white lump on its side(abdomen), I have noticed it in the last 2 days. it doesn't seem as active as it was and doesn't eat as it normally does, (there are 5 other Zebra Danios they seem fine.) it still swims upper/lower levels, Color seems darker than the Zebra Danios
I feed them once every day and do water changes weekly (20%), a water test today indicates all is OK, just a little Alkaline(as usual) Water temp 24 degrees Celsius.
Just wondering what to do next?
Is it a Tumor?
Is it Pregnant?
The size of the fish has not increased

Tank:40G ( 8 months)with 8 red eye tetras, 6 Serpae tetras, 6 Black skirt tetras, 6 Zebra danios and a Cat fish( Algae eater)
I have included the Zebra danios in the last 3 months.
This is the first sick fish I have had.
thanking you in advance.

ANSWER: Hi Greg,
 If it is a distinct lump and it is just on one side, odds are it is a tumor.  Unfortunately, there is nothing you can do about that.  

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


---------- FOLLOW-UP ----------

QUESTION: Thanks Ron,
Would this effect  other fish?
How much longer (on average) has the fish got to live?
Can I do anything to reduce chances of tumor on the other fish?
Is tumor a common desease amount tropical fish?
Is there any research on what may cause tumors in Fish?

Answer
Hi Greg,
  Just as with cancer in humans, tumors are not contagious.  Also, a tumor is not necessarily lethal.  He could live a long time with it.

  Also, like cancer in humans, tumors can be the result of exposure to things in the environment or might be caused by many different things inside a fish.  We know much less about cancer in fishes than we do about cancer in humans.  

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