Improvement of water quality on carp fish farms

Istraživanje djelovanja kalijeve soli (10 mg L-1), hidratiziranog vapna (10 mg L-1 i bakrenog sulfata (0, 2 mg L-1) na biokemijsku potrošnju kisika (BPK24h) provedena su na ribnjačarstvu D. Miholjac, i to u ribnjacima 1a (16 ha), 1b (15 ha) i 1c (15 ha). U ribnjacima se uzgajao dvogodišnji šaranski mlađ u gustoći nasada 12 500 ind ha-1 (625 kg ha-1), 13 300 ind ha-1 (560 kg ha-1) i 12 000 ind ha-1 (780 kg ha-1). Upotrijebljene doze svih primijenjenih kemikalija smanjile su BPK24h, ali različito (tabl. 4). Upotrijebljena pojedinačna doza kalijeve soli u tijeku 24 sata smanjila je biokemijsku potrošnju kisika od 0,27 do 2,5 mg mg L-1 (9-73%), hidratizirano vapno od 0 do 1,29 mg L-1 (0-44%) i bakreni sulfat od 0 do 1,97 mg L-1 (0-44%). Samo primjena kalijeve soli bila je statistički opravdana (P<0,05). Smanjenje BPK24 bilo je izraženije u vrijeme niske koncentracije kisika u vodi.Investigations on the effect of potassium salts (10 mg L-1 1), hydratized lime (10 mg L-1 ) and copper sulphate (0.2 mg L-1) on the biochemical consumption of oxygen (BPK 24 h), were carried out on the fish farm D. Miholjac, in fish ponds 1a (16 ha), 1b (15 ha) and 1c (15 ha). Two year old carp fry (young) were cultured with a stocking density of 12 500 ind/ha-1 (625 kg/ha-1 ), 13 300 ind/ha-1 (560 kg/ha-1) and 12 000 ind/ha-1 (780 kg/ha-1), respectively. The doses given of all applied chemicals decreased the BPK 24h, but diffe¬rently (Table 4.). The individual doses of potassium salts used decreased the biochemical consumption of oxygen during 24 hours from 0.27 to 2.5 mg L-1 (9-73%), hydratized lime from 0-1.29 mg L-1 (0-44%) and copper sulphate from 0 to 1.97 mg L-1 (0-44%). Only the application of potassium salt was statistically justified (P < 0.05). The decrease of BPK 24 h was more expressed in the period when the oxygen concentration in the water was low