As mentioned earlier, it is because they have one of the most complete freshwater collections in the world. An example: Most people that visit public aquarums could be mislead into thinking South American freshwater pretty much only consists of two Amazonian habitats: Flooded forests and blackwater rivers. Sure these are important habitats, but they're only a fairly small percentage of the Amazon, let alone all South American freshwater habitats. If you visit Berlin you'll find both these, but you'll also find South American aquariums aimed at the the Guiana Shield, Orinoco, Xingu River (representing a clearwater river), Pantanal (an unusual wetland that mainly is associated with the Paraguay basin, but in periods of flood also is connected to the upper Madeira/Tapajós basins), Paraguay River (itself part of the Rio de la Plata basin, which I suspect relatively few have heard about despite it having an average discharge similar to the Mississippi+Danube combined), etc. In other words, a much more complete representation of South American freshwater. It's the same with freshwater of other continents, although their coverage of the Nearctic is mediocre (however aquatic fauna from this region overall is quite similar to the Palearctic). The reptile/amphibian sections in the same building are also quite good and do include aquatic highlights such as gharial.
Thanks for this far-reaching answer! This sounds very interesting. I really hope to visit the Aquarium Berlin one day.
Got an answer and Guinness World Records are right: Chimelong's 22.7 million l (6 million gal) ocean tank is much larger than Georgia's 24 million l (6.3 million gal) ocean tank. Why? The Chimelong record is strictly the volume of the main tank, while the commonly quoted figure for Georgia is entire system, i.e. main tank, adjacent rear holding tank, associated filters and pipes, etc. If using comparable figures, Georgia's strict main tank volume is 15.3 million l (4 million gal) and the rear holding tank is an additional 0.3 million l (0.08 million gal). BTW: Providing total system volume (including water in associated filters, pipes, etc) isn't unusual. The numbers provided by many aquariums are actually total system rather than strict tank volume.
I believe Nausicaa Centre National de la Mer (France) may now deserve a place on this list [10 million litres], and I've been trying to work out whether Chiang Mai Zoo's Aquarium makes the cut - I think the main saltwater tank should be about 4 million litres, but I've seen '8 million' quoted, so perhaps the freshwater tank has a similar capacity?
Another addition to the list is the main tank in Gran Canaria's wonderful Poema del Mar aquarium, which has a volume of 5.5 million litres.
