| 摘要 |
PCT No. PCT/DE96/00685 Sec. 371 Date Dec. 16, 1996 Sec. 102(e) Date Dec. 16, 1996 PCT Filed Apr. 18, 1996 PCT Pub. No. WO96/33137 PCT Pub. Date Oct. 24, 1996In the present state of art, use is made of aqueous mixtures of sodium phosphates, preferably mixtures of pentasodium triphosphate (for softening) and sodium dihydrogen phosphate (to reduce the pH) of hard and slightly alkaline water in aquaria to values acceptable especially for ornamental tropical fish. This inherently effective preparation for softening and acidifying the aquarium water leads, however, to the clouding of the water after a short time and to chalk flocculation, while the hydrolysis of the triphosphate results in an increased level of orthophosphate which is particularly favorable to the growth of algae. The invention prevents these drawbacks by the use of phosphonic acid compounds which complex the alkaline earth metal ions determining the hardness of water. Preferred phosphonic acids here are ethylene diamine tetra(methylene phosphonic acid) and its pentasodium salt and diethylene triamine penta(methylene phosphonic acid) and its heptasodium salt. The complexing phosphonic acids may be used alone or in a mixture.
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