The Effect of pH and Mineral Content of Fe, Ca, Mg, And Cl On The Growth of Koi Fish (Cyprinus carpio) in Aquariums with Water Sources of The Tuntungan River in Medan

The effect of pH and mineral content of Fe, Ca, Mg and Cl on the growth of koi fish (Cyprinus carpio) in an aquarium with water sources of the Tuntungan Medan river has been studied. Cultivate koi fish in the aquarium with water from the Tuntungan river had various pHs between 5 to 10. NaH2PO4 is used to reduce pH level, while NaHCO3 is used to elevate pH level.  Before the fish was placed, the mineral content of Fe, Mg, Ca, and Cl in the water after pH arrangement was analyzed. The initial weight of the fish that will be incorporated into each aquarium was weighed. After ten days, the fish were weighed, and the mineral content of Ca, Mg, and Cl were determined by titration method, whereas Fe mineral was determined using the Visible Spectrophotometry method. The same thing is done on days 20, 30, 40, and 50. The results showed maximum growth at 120.50% of fish in the river water aquarium pH = 8.5 with high levels of iron (Fe) which fluctuated between 0.4343 mg / L - 0.6020 mg / L, the level of calcium (Ca) which fluctuated between 7.76 mg / L - 15.52 mg / L, the levels of magnesium (Mg) which fluctuated between 120.28 mg / L - 157.14 mg / L, and levels of chloride (Cl) which fluctuated between 27.99 mg / L - 32.48 mg / L. Minimum growth in amount of 88.02% found in the river water aquarium pH = 5.5 with the levels of iron (Fe) which fluctuated between 0.2246 mg / L - 0.5610 mg / L, the level of calcium (Ca) which fluctuate between 7.76 mg / L - 27.93 mg / L, the levels of magnesium (Mg) which fluctuated between 80.71 mg / L - 108.64 mg / L, and levels of chloride (Cl) which fluctuated between 17.99 mg / L - 39.98 mg / L. Water with pH = 9.5 is not suitable as a medium for the cultivation of koi fish.