what the @%^^&$^ am I doing wrong????

[banditpowdercoat]

I seem to not be able to keep Puffers??? Brought home a foxface, Lionfish and Puffer on Thursday. The Lion and puffer were in the same tank at JL. Acclimated them for over an hr. Puffer was swimming fine when we put him in, checking the tank out etc. Yesterday, I don't see him. Foxface and Lion are out but figure puffer is hiding. Today, find him in the closed loop return. Theres not alot of suction in the CL return as I have 4 inlets, so I don;t think he just got stuck. This is my 3rd puffer I have tried and lost within a week of acclimating?? All the other fish are fine. What the heck am I doing wrong? We want one SOOOO bad.