Dead Cory - Internal bleeding?
 

Ammonia - 0.25 (Probably from the dead fish? I am performing a 50% pwc as soon as this is posted.
Nitrite - 0
Nitrate - 10
PH- 7.2

I found a dead albino cory in my catfish tank this evening. My girlfriend said that it was alive and kicking when she fed the fish this morning. She also said that it wasn't moving around much. There is a huge bruise across its stomach area. I have attached a photo of its corpse (ewwie!)

I have never seen anything like this... It looks like internal bleeding? Any thoughts? There are fry in a breeder net in that tank, so hopefully there isn't an epidemic. This is my most successful breeding attempt to date!!!!

http://img7.imageshack.us/img7/1230/mmspicture2z.jpg

PWC done - Ammonia is reading 0 and Nitrate is reading at between 5 and 10

None of the other stock in that tank are showing any symptoms or acting odd.



BTW - Almost forgot -

10 gallon
Aquaclear 30 filter

Stock-

Albino cories - 3 (was 4 until a bit ago) :(
Otos - 5
And a breeder net full of fry - about 4-5 days old. They are moving to a 10 gallon nursery setup once they are ready.



Did I leave anything important out?

Could it be possible that stress from birthing may have resulted in complications? Could substrate be too rough? I'm no expert and this is only speculation but were it me,, I might slowly lower the temp in the tank over a couple days to slow down possible bacterial pathogens which develop faster at tropical temps as opposed to cooler temps and cory's that I have kept often did much better at 74 degrees rather than warmer water.
Might also consider sand for substrate which is much smoother than rocks,gravel.
Might also try offering shrimp pellets,spirulina pellets,and perhaps hold off on blood worms for a while and try flake foods or small pellet foods high in protein. New life spectrum and Ocean nutrition make some very good foods. Might also consider medicated foods if other fishes begin to show symptoms.
Hope some of this helps.
P.S. might also consider placing the heater halfway up the glass in the tank if it is near the bottom where fish can wedge themselves between the heater and the glass while resting or trying to avoid the advances of perhaps numerous males. Just some thoughts.

Internal bleeding etc can be a secondary infection,
as in intestinal worms causing the damage,

Blood settles after death, that's most likely what you're seeing here. bruising can also occur post mortem as capillaries and blood vessels break down allowing blood to leach into the surrounding tissue.

Unless the bruise was seen before death I wouldn't consider it a contributing factor.