@ Bernd: I have my 1.2 P. phoenicurus in these water parameter: EC 24 (after water change) – 35(before water change) , pH 4,2 – 5.2, dKH <1, temperature 26°C, after water change 24°C. Tank size is 25x40x25cm.
pH mostly ca. 4,7,
@Arno: very fine! And you have found the eggs! Will you breed the larves outside the parents tank?