The reason 55g are so popular is for fresh water.
For the most part, i think that tangs and triggers need the length of the tank to be happy. However, they are somewhat messy and the added water gives for a greater capacity to dilute nitrates.
Which is why some people believe a 55g is good enough for a tang (4 feet long). As some have suggested, maybe getting a smaller one and trading it back in when it gets larger is an option.
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40g with 10g sump with ~85 lbs liverock, 1.5" deep livesand bed.
Fish - halloween hermits, blue leg hermits, left-handed hermits, emerald crabs, assorted snails, chocolate chip star, 4x strawberry conches, tuxedo urchin x2, electric flame scallop, gold stripe maroon clown, blue-side wrasse, yellow tang, yellow watchman goby, white seabae anemone.
Coral - One lonely Kenya Tree. | 
