From Vienna's site, which does a pretty good job listing all their species, I got the following species numbers: 43 reptiles, 20 amphibians, 119 fish and 73 invertebrates.
The Rainforest House has side enclosures for Burmese python, vampire crabs and some frogs. There are also a few tanks for rainforest fish: eyespot pufferfish, giant gourami, archerfish and mudskippers. Most notably, however, are the displays of rock frogs and northern river terrapin, for both of which Vienna acted as a pioneer to keep them in captivity.
The Insectarium displays most of Viennas insects, and is one of the better insect houses I've been to, with only ARTIS' coming close.
The Aquarium and Terrarium House houses almost all of Vienna's herps and fish. Highlights here are the reef tank, the Crocodile Pavillion, the breeding of endangered fish species, the rhinoceros iguana/Haitian ameiva terrarium, the stingray/caiman lizard terrarium and the lovely outdoor terrariums.
Even though there are other ectotherm enclosures dotted around the zoo, the final major ectotherm habitat is the Desert House. Highlights here are black-tailed rattlesnake, angulate tortoise and armadillo girdled lizard.
Coincidentally, all ectotherm conservation also counts as aquatics, so I've detailed their conservation and research efforts
here already.