Since when am I the only one recommending these sizes?
From *****
Though Zebrasoma are somewhat smaller and less free-ranging than other Acanthurid species, these tangs require large amounts of tank space to be at their best. A fifty-gallon tank is the absolute smallest I'd keep one in.
and from the ULTIMATE tang police, ***** in a pinned topic (reference Scott Michael, Marine Fishes, 500+ Essential-To-Know Aquarium Species, Microcosm Ltd., 1999
# Acanthurus achilles, Achilles Surgeonfish, 100 gal (380l).
# Acanthurus coeruleus, Atlantic Blue Tang, 75 gal (285l).
# Acanthurus japonicus, Powder Brown Tang, 75 gal (285l).
# Acanthurus leucosternon, Powder Blue Tang, 100 gal (380l).
# Acanthurus lineatus, Lined or Clown Surgeonfish, 180 gal (680l).
# Acanthurus nigricans, Whitecheek Surgeonfish, 75 gal (285l).
# Acanthurus olivaceus, Orangeshoulder Surgeonfish, 135 gal (510l).
# Acanthurus pyroferus, Mimic Surgeonfish, 75 gal (285l).
# Acanthurus sohal, Sohal Surgeonfish, 180 gal (680l).
# Acanthurus tristegus, Convict Surgeonfish, 75 gal (285l).
# Acanthurus tristis, Indian Mimic Surgeonfish, 75 gal (285l).
# Ctenochaetus hawaiiensis, Chevron Tang, 100 gal (380l).
# Ctenochaetus strigosus, Kole's Tang, 75 gal (285l).
# Naso brevirostris, Spotted Unicornfish, 180 gal (685l).
# Naso lituratus, Orangespine Unicornfish or Naso Tang, 135 gal (510l).
# Naso unicornis, Bluespine Unicornfish, 200 gal (760l).
# Paracanthurus hepatus, Pacific Blue Tang, 100 gal (380l).
# Zebrasoma desjardinii, Indian Ocean or Red Sea Sailfin Tang, 135 gal (510l).
# Zebrasoma flavescens, Yellow Tang, 75 gal (285l).
# Zebrasoma scopas, Brown Tang, 75 gal (285l).
# Zebrasoma veliferum, Sailfin Tang, 135 gal (510l).
# Zebrasoma xanthurum, Purple Tang, 100 gal (380l).