SOME PRINCIPLES AND PRACTICES OF 



WATER MANAGEMENT FOR MARINE AQUARIUMS 



By James W. Atz, Curator 



New York Aquarium, New York Zoological Society, Brooklyn, N.Y. 



Abstract. — Instability of sea water and its organic constituents, when confined in 

 aquariums or circulatory systems, and the characteristic inability of marine organisms 

 to adjust to changes in their environment, combine to make the keeping of marine life 

 in captivity a difficult procedure. The maintenance of sea water in suitable condition 

 depends upon a chemically inert water system, a low ratio of animal life to volume of 

 water, the control of bacteria, and the elimination of metabolic waste products. Methods 

 used to accomplish this include aeration, filtration, storage in the dark, and treatment 

 with alkalizers, ultraviolet light, and antibiotics. 



Despite a tradition that goes back to the 

 ancient Eomans and a lively, uninter- 

 rupted history of more than a century, the 

 keeping of marine animals in captivity 

 remains more of an art than a science. 

 The most valuable attribute an experi- 

 mentally minded marine biologist can have 

 is a wet thumb. Of course, the more he 

 is able to apply precise, reproducible tech- 

 niques to the maintenance of his subjects, 

 the greater are his chances of success, but 

 there will inevitably remain some intangi- 

 bles, indescribable and unpredictable, that 

 he, as scientist, can only attribute to the 

 complexity of the subject he is dealing 

 with. 



Central to the problem of keeping ma- 

 rine animals alive in aquariums is the 

 maintenance of sea water in such confined 

 bodies. In his classic elucidation of the 

 coordinate roles played by the fitness of the 

 environment and the fitness of the indi- 

 vidual in the evolution of life, Henderson 

 (1913) points out that in no other habit- 

 able place on the earth are so many con- 



The author's present address is American 

 Museum of Natural History, New York, N.Y. 



ditions so stable and so enduring as in the 

 ocean. This eon-embracing stability of 

 the sea as an environment of life is the 

 fundamental cause of the difficulties that 

 marine laboratories, public aquariums, 

 and home aquarists alike have in keeping 

 marine fishes and invertebrates. Because 

 these animals evolved in a world that has 

 remained practically constant in tempera- 

 ture, osmotic pressure, alkalinity, and 

 chemical composition, they have developed 

 few mechanisms to isolate themselves from 

 these environmental factors and little 

 tolerance for change. In captivity, they 

 perforce must be provided with an en- 

 vironment that at least approaches in sta- 

 bility their natural one. But once sea 

 water has been removed from the ocean, it 

 begins to change and to lose some of its 

 capacity to support delicate marine life. 

 This is directly and indirectly the result 

 of its no longer being part of a body of 

 water that is to all intents and purposes 

 infinitely large. The best that any marine 

 aquarium, practices seem to be able to do 

 is merely to slow down the rate of this 

 deterioration. 



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