Fahaka puffer. Most docile fish ever had. It literally sat in his cave or under the sand all day every day. Barely ate even when giving the best foods like live crayfish, crabs, king frozen prawns, mussles, squid you name it.
Gave him a 150g as well and only used a fraction of it. The live crayfish ended up being tank m8s. Lived with a few other community fish and some cichlids and left them alone. When it was time to move him he had no reaction whatsoever .. everything seemed to not bother it ... i think maybe was a zombie puffer