I see a lot of people suggesting 125G+ tanks for some of these species listed above, however that is the size you will need if you plan to house them for its entire life. If the fish you have are small and you want to fit another one go for it, its your tank, just be prepared to move them to a larger tank when they get bigger. Triggers generally grow very slow IMO
, puffers do not, and can grow around 3+ inches in 6 months. You can go on pretty much any saltwater forum and find someone on every thread disagreeing about tank sizes, just ignore it and do your own thing, just be responsible and make sure you bump up the tank size when the fish get bigger.