Don't Know Whats Wrong..

[Kat787]

Bought a bigger fish tank, 10 gallon upgraded from 3 gallon, set it up the way it should be, treated the water and rinsed everything with just water. I had 6 tetras, acclimated them properly and put them in the bigger tank. One of them started floating around like he was dead, but it was still alive so I removed it from the new tank and put it back in the old tank. Checked on all fish in the morning and the 5 remaining in the new tank had all died and the one in the old tank was back to normal. Did a partial water change and left it for a couple day. Thought things would be fine so I went and got two mollies, they also gave me nutrafin cycle to help build bacteria, tried putting them in the new tank, along with the remaining tetra and same thing started happening to all of them, acting lifeless floating around the tank. As soon as I noticed them acting this way I put them back into the old tank where they seemed to recover and be fine. Have tested the water daily and all levels have been good. Let the new tank cycle for a couple more days, tried putting them (tetra didn't survive so only two mollies now) in again and same thing. I have tried pretty much everything I can think of and no luck. I am out of ideas on why this keeps happening. Help!

 

[BiggTexx]

Have tested the water daily and all levels have been good.

What is your definition of good and what is that compared against?  Can you post all of the readings for us to understand what you are working with?
 
As a minimum:

• Ammonia
• Nitrite
• Nitrate
• pH
• Temperature

 
 

Let the new tank cycle for a couple more days

How long was the original cycle and which method was used?

 

[Kat787]

Ammonia - 0
pH - 7.4
Nitrite - 0
Nitrate - 10

Put in some water from old tank and media from filter

 

[BiggTexx]

What about the temperature?
 
If you moved from a stable tank to a stable tank (meaning temperature, pH and everything else are equal), there would be no real reason to acclimate.
 
How did you verify the cycle? Did you add pure ammonia or any other method to add ammonia (fish food), etc?
 
Quick deaths (within 24 hours) are most notable from pH and thermal shocks.

 

[Kat787]

Temperature is the same in both.

Added fish food