Disappearing Fish

[Autonerd]

Hi all -- I have an established 15 gal tank (you helped me establish it!) that's about 2 yrs old. I started with six neons, six pygmy corys and a couple of ghost shrimp. The ghosts are gone, cory population has dropped to 2 and neons to three. I also have a small MTS population (so much for getting plants from the LFS rather than the chain store!) and, as a result, three assassin snails.
 
I suspected one ghost of the fish disappearances, but he's gone now, so I decided to start re-stocking to get back up to a half-dozen. Over the past couple of weeks, I added three (tiny) pygmy corys and four neons. One of the neons died right away, but I didn't see any aggression...
 
...except all three of the pygmys and two more neons have disappeared.
 
There's no trace of the pygmys, although I did just find what I think are the remains of a neon at my last water change.
 
My chemistry levels have been good and I haven't seen any signs of aggression or fin-nipping... but something is killing (and eating) the fish. My tank is like an Agatha Christie novel!!
 
Any idea what could be killing the fish? Is there a better way to restock? Am I better off leaving the fish in small numbers or getting a large school going?
 
Any advice is appreciated - thanks!

 

[bluesword23516]

Does the tank have a lid? 

 

[Autonerd]

Does the tank have a lid? 

Yes, and I haven't found fish bodies... we have a dog but she's a picky eater. 

 

[Ninjouzata]

Can you give exact water parameters? Is your test kit still good? How did you acclimate the fish?

 

[DerpPH]

what filtration system do you use?

 

[Autonerd]

Two mature fish have just died, so I moved this to the Emergency forum:
 
http/www.fishforums.net/index.php?/topic/433687-die-off/
 
Fish Herder, I use an AquaClear 30. Fish acclimation: Floated fish in bag in water, then added some of my tank water every 10 mins or so, and eventually netted fish into tank. I did *not* test the water in the bag before I added the fish. Test kit is 2-3 years old.
 
Aaron