Dead Fish

[Fantast Bronson]

When I got up the morning I found 1 of my Male Neon Blue Gourami's and 1 of the Chinese Alge Eters ( the small 1) Dead behind the filter . There was no sign of illness or any thing, so I'm a bit pusseled
For about a months ago I had a serious situation in my tank. I lost about 12 fish in 24 hours, but since then there have been no problems, but mu male Gold Gourami who thinks he "Mister Mean", and that seems to have improoved over the last couple of days
Every thing in the tank seems to be
pH 6,6
NH3/NH4 : 0
No2: 0
NO3: 0
Temp 78 F

But as I'm still new to the "fishy buisness" I would like to here any surgestions to what might be wrong.
Thanks

 

[Chasing Puck]

Is the tank planted? Otherwise, it's a bit odd for the nitrates to be 0.

Just off hand, I'd worry about aggression--several fish that should be fairlly large in there, and they might be trying to push the other fish out of their territory.

 

[Shizat]

Having 0 readings of nitrate,nitrite, and ammonia is kind of weird unless you are doing a crazy amount of water changes or have massive amounts of plants.

 

[kent]

did u add any new fish? coz the new fish may have introduced parasites/infection, which caused the deaths.. if you didnt add any new fish. I would still guess it's because of a disease..It's really hard to diagnose fish with infection..so my suggestion is to observe your other fishes..