My neons (some of you may have seen the 1800 fish in one tank thread) are crashing by the dozens. Otocinclus and hatchets are unaffected as are all the contaminant pencil fish. The neons turn upside down, go pale, float to the surface and die. Ammonia 0, nitrite 0, nitrate 10, temp 75. Filter is an xp3. 50% daily water changes. These fish came in from import sunday (arrived in teh country saturday). I put a fully cycled and established filter (the xp3) from my 75g discus tank as well as all the rocks and gravel from my 55g Oscar tank. There have been no fluctuations. I have no idea what is going on here. They are literally dropping (well floating) like flies by the dozens each minute. Does ANYONE have any advice? I put purigen in the filter in case it was a contaminent (though i would think the hatchets and the otos would be effected as well). I am distraught, freaking out, and devestated. Please give advice