Maretarium is a public aquarium opened in Kotka in 2002 , located on Kotkansaari , on the shores of Sapokanlahti . It has focused on the presentation of Finnish fish species and water bodies . There are about 60 native and permanent fish species from Finland. Maretarium was created in co-operation between the City of Kotka, the University of Helsinki and the Game and Fisheries Research Institute . In addition to aquariums, there are also facilities for researchers and a nature school. The house also has a maritime theater, a café Meri Cafe Kristina and souvenir shop.

Pools 

The Maretarium has a total of 22 themed aquariums, the largest of which is the Baltic Sea Pool. It has four windows, one of which is the high glass wall of the maritime theater. The cylindrical basin holds about 500,000 liters of water. Its depth is seven meters, which corresponds to the average depth in Finnish lakes. It is not covered, so the sunlight can freely shine there, and therefore it grows a wide variety of filamentous algae. They are allowed to grow in it as they feed on the smallest aquatic organisms, which in turn feed on the smaller fish in the pool. The basin was renovated, after which it began to leak. The opening of the maretarium will be postponed due to a leak. 

The maretarium has even smaller pools, Saimaa , Kymijoki , the Gulf of Finland , lakes in Central Finland, Lapland waters, River / pond , Outdoor pool. The theme in the basins is therefore the biotopes of Finnish waters .

Threatened Species 

The maretarium has about 60 species of fish as well as seafood for a total of more than 1,700 individuals. Maretarium fish have been sourced from all over Finland. The majority of salmonids come from the fish farms of the Finnish Game and Fisheries Research Institute, including Laukaa and Taivalkoski. Some of the roach fish are part of the management and experimental fisheries at the Uusimaa and South-East Finland environmental centers. Fish and scallops have also been obtained from fishermen and divers in the Kotka region, and the staff has also supplemented the species. 

In summer, there are also small aquatic animals, such as water lizards, snakes and frogs, in terrariums and pools. In the winter, they are dormant in the basement.