On the nitrogen cycle and cultivable capacity of fish in the balanced aquarium By Aritsune SAEKI

On the nitrogen cycle and cultivable capacity of fish in the balanced aquarium By Aritsune SAEKI

Fig. 1 Percolating apparatus

Table 1. Water quality of the balanced aquarium. Capacity of tank : 130 1. Cultured fish : about 30 g. of tropical-fish. Plant : 0-150 g. of MyrioPhyllum, Cabornba, Vallisneria or Hygrophila.

Fig. 2 Nitrogen cycle in the balanced aquarium.

Fig. 3 Nitrification by percolating procedure Sand : 65g. weathered granite sand 2-5 mm in size from the bottom of the balanced aquarium. Water : 1.5 1. well-water added ammonium sulphate. Circulating velosity is about 150 cc per minute by air lift. Water temperature 21 Ž.

Table 2 Exchangeable ammonia of bottom sand of the aquarium Table 3 OrgEnic nitrogen content of the aquatic plants

Table 4 Denitrfication in the balanced aquarium (1956) Aquarium tanks are the same as Table 1

Table 5 Velosity of nitrogen compounds removing from the water by nitification, assimilation and denitrication in the balanced aquarium. Nitrogen N ć/1/day/100 cm2 bottom area. Bottom is covered with 2 `5 mm sand O. 5 cm in depth. 3. 6 grams plant (10 cm long Cabomba and Hygrophila) is contained in a litre and grows 7. 2 g a month.

Fig. 4 Cultivable fish capacity in the balanced aquarium. 1) KUHL, H. and H. MANN : Arch. f. Hydrobiol. Suppl. 22, 1955. 2) \ : Z. f. Fischerei, 4, N. F., H. 3/4, 1955. 3) \ : D. A. T. Z., 9, 99-120, 1956. 4) \ : D, A. T. Z., 9, 125-129, 1956. 11) LEE, H. and. T. H. QUASTEL, : Biochem. J., 40, 803-828, 1946.

12) INNES, W. T. : Exotic Aquarium Fishes. Pub. Comp. 11th ed., 1952. 13) WELCH, P. S. : Limnology, MCGROW HILL, 1952. SUMMARY The nitrogen cycle in the balanced aquarium was studied in regard to the secretion of nitrogen compounds by fish, nitrification, denitrification, and assimilation by plants and bacteria. And then cultivable capacity of fish was estimated. When the initial content of ammonia in the water is A, secreted nitrogen compounds from fish F, nitrogen nitrified by bacteria x1, nitrogen assimilated by bacteria x2, by aquatic plants x3, denitrified nitrogen x4, and the ammonia content at a given time t is M : When fish is cultured in the healthy and normal condition, 100 grams fish secrets 50 mg of nitrogen compounds per day. When the bottom of the aquarium is covered with either calcite or weathered granite sand 25mm in size, the velosity of nitrification by bacteria growing on it is 240 ć per 100 cm2 per day. And, nitrogen assimilated by bacteria is 170 ć per day, if the bottom of aquarium is made clean occasionally. When 1 litre of water contains 1 shoot of Cabornba and Hygrophila 10 cm long respectively, which grows three times in length during a month, nitrogen assimilated by them is 250 ć per day. Denitrification is determined by measuring the ratio of argon to nitrogen gas. Its velosity per litre is 16 ć per day. From these data, the velosities of nitrification, assimilation and denitrification in the aquarium are 76-674 ć/day, as shown in Table 5, and cultivable fish in that is given in Fig 4.