Overview
The southern tip of the African continent is the meeting place of two mighty and bountiful oceans, the Indian and the Atlantic. The Two Oceans Aquarium is ideally positioned to showcase the incredible diversity of marine life found in these two oceans.
Our Indian Ocean exhibits are home to vibrant tropical beauties from the warm Indian Ocean. Our exhibits include the very popular interactive Western clownfish (AKA Nemo) exhibit, honeycomb, floral and geometric moray eels and a coral exhibit. This gallery also features a 3m-wide cylindrical exhibit showcasing the dazzling colours of Indian Ocean fish.
Our cold Atlantic Ocean exhibits include cryptic fishes playing hide and seek; translucent jellies and the shy master of camouflage, the common octopus. We also showcase the endemic, endangered Knysna seahorse and an overseas visitor, the alien-like Japanese giant spider crab.
The cold Benguela Current
Off South Africa's west coast, the cold Benguela Current flows sluggishly northwards. Here, biological production is high and species diversity is low. Planktonic animals (zooplankton) feed on the phytoplankton, and are in turn eaten by filter-feeding fish such as pilchards and anchovies. The west coast is one of the richest fishing grounds in the world, supporting huge commercial fisheries and large colonies of Cape fur seals and endangered African penguins.
During summer, strong south-easterly winds blow along the coastline, resulting in upwellings of icy cold, nutrient-rich water. The phytoplankton flourish and and prolific forests of giant kelp plants dominate the shoreline.
The mighty Agulhas Current
The Agulhas Current, one of the most powerful currents in the world, flows southwards down the east coast of South Africa, bringing warm Indian Ocean water from tropical regions.
The coastal waters are warm, generally clear and low in nutrients.
Diversity is the name of the game on the east coast and a great variety of colourful fish, such as butterflyfish, damsels, surgeons and angelfish add spice to life on the reef.
Although there is great diversity on the east coast, the population size of each species is restricted due to fierce competition for food, limited space on the reef and a high number of predators.
Rainbow nation on the reef
Tropical fish use colours as flags or advertisements. Some colours warn of danger and others advertise cleaning services. Patterns and colours also help to camouflage the fish, making it difficult for predators to see its true shape amongs corals and sponges. Some species even mimic others!
Ancient associations
Coral reefs are formed over millions of years and are found in the warm oceans of the world.
Corals are not plants or even rocks. They are colonies of small animals, known as polyps, living closely together with minute single-celled plants called zooxanthellae. This is known as mutual symbiosis as both the corals and the zooxanthellae benefit from the association.
The corals receive "food" from the zooxanthellae when they photosynthesise and in return the corals supply the zooxanthellae with ammonia and phosphate from their waste metabolism.
The transfer of these waste products to the zooxanthellae is crucial for their survival as inorganic nutrients are almost absent in the surrounding water.
Corals under threat
The world’s coral reefs are under threat. Coral bleaching is caused by increased sea surface temperature, high levels of ultra-violet light, high turbidity, sedimentation and abnormal salinity. The algae that live in the polyps die and the corals turn white, becoming more vulnerable to overgrowth, disease and reef organisms that bore into the coral skeleton and weaken the reef structure.
You can help!
Human activities are the major threat to coral reefs: Pollution, overfishing, destructive fishing practices, collecting it for the aquarium and jewellery markets and mining it for building materials damage reefs. Please do not buy coral jewellery or ornaments. If you swim, dive, fish or snorkel on a coral reef, please don't touch coral and don't take souvenirs.
Poisonous or venomous – what's the difference?
Venomous animals cause illness or death by "injecting" a toxin into their prey or attacker. Firefish and stonefish are venomous animals.
Poisonous animals have poisonous flesh or poison glands in their bodies. These animals do not "inject" the poison, but the poison is transferred if the flesh is eaten or if it comes into contact with the skin. Pufferfish are poisonous animals.
