There are a few nice things at Akva-Tera but if you only have one day I'd recommend you stick to the zoo. Akva-Tera is hard to stretch out for more than half an hour but would cost you at least a couple of hours of zoo time.
The times I've done both it's typically been Akva-Tera the evening before the zoo.
I'd agree with that 100%. This is the species list of what I saw last week at AkvaTera, plus what was signed but not seen:
• Baron's green racer (
Philodryas baroni)
• Blue poison dart frog (
Dendrobates tinctorius var. "Azureus")
• Blue-spotted tree monitor (
Varanus macraei)
• Caiman lizard (
Dracaena guianensis)
• Chinese gliding tree frog (
Zhangixalus dennysi)
• Common treefrog (
Polypedates leucomystax)
• Duméril's madagascar swift (
Oplurus quadrimaculatus)
• Emerald skink (
Lamprolepis smaragdina)
• Fiji banded iguana (
Brachylophus fasciatus)
• Folohy Golden frog (
Mantella laevigata)
• Golden poison frog (
Phyllobates terribilis)
• Greater Madagascar day gecko (
Phelsuma grandis)
• Green basilisk (
Basiliscus plumifrons)
• Green tree python (
Morelia viridis)
• Indonesian forest dragon (
Lophosaurus dilophus)
• Julio's casquehead iguana (
Laemanctus julioi)
• Lake Urmia newt (
Neurergus crocatus)
• Lined Seahorse (
Hippocampus erectus)
• Mata-Mata (
Chelus fimbriata)
• Neotropical painted wood turtle (
Rhinoclemmys pulcherrima)
• Pajama cardinalfish (
Sphaeramia nematoptera)
• Palette surgeonfish (
Paracanthurus hepatus)
• Radiated tortoise (
Astrochelys radiata)
• Sakishima grass lizard (
Takydromus dorsalis)
• Spotted archerfish (
Toxotes chatareus)
• Spotted sailfin suckermouth catfish (
Pterygoplichthys gibbiceps)
• Spotted scat (
Scatophagus argus)
• Standing's day gecko (
Phelsuma standingi)
• Western bearded anole (
Anolis barbatus)
• Western twist-neck turtle (
Platemys platycephala)
• White-throated gecko (
Gonatodes albogularis)
• Yellow-banded poison dart frog (
Dendrobates leucomelas)
• Yellow-headed day gecko (
Phelsuma klemmeri)
Signed, not seen
• Green toad (
Anaxyrus debilis)
• Karsten's girdled lizard (
Zonosaurus karsteni)
• Marine toad (
Rhinella marina)
• Okinawa sword-tail newt (
Cynops ensicauda popei)
• Panther chameleon (
Furcifer pardalis)
• Prehensile-tailed skink (
Corucia zebrata)
• Sabana surinam toad (
Pipa parva)