I hate to repeat others but,GBR.
I know many of you are going to have NO sympathy for me,or take this seriously.
For me they live in the fishroom.
Not one in my DT and I have added a few!
I need to set 'some' aside and see how long they really last.
I have had WAY BETTER success keeping the 'forbidden Mandarin Goby' in every marine tank I have had since the 1980's!
With most of them(mandarins) lasting 4-6 years.
I still think 2 years for a GBR is a long life but such a short time in my tanks!
It is this disappointment and difficulty that drive me to keep trying.