Help! Weird Thing Killing Fish!

[dundadundun]

^ oh, absolutely. just like trying to deep siphon all of the gravel in a tank at the same time can bury the beneficial bacteria on the surface and release any gases/grime underneath. not good...

 

[oo7genie]

Wait wait, are you guys messing with me or something? Earlier in this thread ur saying 0 was bad???? I think im gonna stick to listening to my father, listening to you guys gets me too confused.

Everyone here is saying the same thing. You simply misread trItes, and thought they meant nitrAtes.

As far as the 3 main parameters you should monitor aside from pH are concerned, it's very simple, and this is what everyone here is saying:

0 ammonia = good
0 nitrites = good
0 nitrates = bad

on the flip side

nitrates through the roof (triple digits) is said/thought to be bad
any nitrites at all = very bad
any ammonia at all = very bad

Check your ammonia. If you have measurable nitrIte, you may have ammonia. Especially, because dead fish are one of the fastest producers of ammonia in a tank. It's entirely plausible that the second fish that died, did so as a result of an ammonia spike brought on by the first fish's death.