Now what!?

[Melaniew55]

So I have upgraded from a ten gallon to a 55. First I added partial of the old filter media into the 55. After two days ammonia/nitrite/nitrate were all 0. Moved over the HOB filter to the 55 gallon to run along side the canister to help get the bacteria in. I then moved my other fish. I have 3 tetra, 3 loach, and 2 baby albino pleco. One loach died this morning, so immediately I tested. 0 everything again. I did noticed the other day when I put it in the tank it had a huge belly but I thought it was eggs after researching.
Now, I have lost one pleco.
Not sure what I am doing wrong. Temp is good, brought over all the media from the old tank. Same fish from previous tank. 0 readings on everything. Ideas? I was hoping to really not loose any of them of course! ?

 

[Aiken Drum]

To kill fish so quickly, most likely cause is temperature or pH shock. You say the temp is ok, but is there a temperature difference between the 2 tanks or could there have been when you moved the fish. Is there a pH difference between the 2 tanks? Did you acclimate the fish when moving them the same as you would when buying new fish?

 

[Melaniew55]

The temp was within the same range and I did acclimate. It may have been the PH. I did not test the old tanks Ph before moving them. The other fish all seem to be doing good.