F8 puffer help

[Vivepopo]

I recently purchased an f8 puffer at my lfs and introduced him to a fully cycled tank. He lasted about a week before he died. The tank I put him in had another smaller f8 puffer who's been in there for about 2 months happy as can be. I had the puffer qt for about 3 wks before I introduced him into the tank. He looked fine at the lfs and did eat the first day I introduced him in the tank that's where it went bad. I fed him blood worms ghost shrimp small snails and both puffers even shared a small crayfish, I don't know what went wrong maybe somebody can help me .
I had him in a 20 g/h tank
Ph 7.2
No2-0
No3-.25
Am-0
Sg 1.002
I'll upload a link to you tube with the video of my puffer

 

[Terrance]

After the first meal, did your new f8 eat anything afterwards? Waiting for the link.

 

[Only200]

Oh he's like a little puppy

 

[Vivepopo]

After the first meal, did your new f8 eat anything afterwards? Waiting for the link.

After the first meal he was fine
Had a problem with the vid sorry.

 

[smomus]

Wanting to start my own f8 build. Following along for any good info.