Vanishing Leapord Danios

[TheSuperdux]

I have been keeping fish for years, various communities including malawi cichlids, and currently an asian themed tank. I have a problem though which is baffling me at the moment. Its a 4ft tank with 2 opaline gouramis, 3 bosemani and 2 banded rainbowfish, 3 khulli loach, 3 yoyo loach, 4 threadfin rainbows. I recently purchased 2 zebra loach and 12 leapord danios. The zebras are being aggresive towards the pakistanis which I am monitering, so far no injuries or damage, they just seem to harrass and fight a bit. The problem is though, I am losing 1 leapord danio a night, I now have only 4 left. The largest opaline gourami is aggressive towards the other but doesnt seem bothered by the other fish. There are never any traces of danio, and there is no way for the fish to jump out and escape. Something is killing them and eating them during the night. My suspicion would be either the opaline gourami (as the largest fish) or the zebra loaches, but they dont seem large enough to do this. Any ideas

 

[WILDER]

What are your water stats in ammonia, nitrite, nitrate, and ph.

You will have to think about rehoming the danio's or the pakistanis, if they carry on being aggressive.