Unexpected Fish Death

[sbundy]

hello

my tank has been up and running now for about 6 months with all these fish inside:

2 red torpedo barbs(now about 2.5 inches)
2 red rainbows(now about 2.5 inches)
1 boesmani rainbow(now about 2 inches)
2 rosy barbs(about 1.5 inches)
1 silver molly(about 1.5 inches)
2 blue jack demphseys(about 1 inches)
2 clown loaches(about 1.5 inches)

i do regular 25% water changes every month. my parameters are and have been perfect. amonia 0 nitrites 0 ph about 7 and nitrates about 20

today one of my red torpedo barbs was dead, he had a chunk missing from his lower body. they are and were all in perfect health. what happened? is there a disease that eats a chunk of body like that or someone also all of them are suddenly pooing(sorry bout the expression) at the same time and lots of white particuls are showing. could it be the chunk of the fish that i couldnt find that they all ate? im a little worried. please help!

 

[snowyangel]

Jack dempsey are aggressive and should not be in a community tank, not to mention they grow to 9 inches and by that time will have made lunch out of the rest of them. I'm not sure if thats what did this but it's a sure possiblity. You can view their profile here to learn more: http/www.fishforums.net/index.php?showtopic=46454