Temperature and water chemistry for M.spechti tank

Hi everybody,

I'm an Italian killifish breeder with the passion for Labyrinths, too!
I'm sorry but I don't speak German, so I can only write in English (I use Google Translator to read German)...

Now in my tanks I'm successfully keeping Ctenopoma acutirostre and Channa gachua TH3/02 (not in the same tank ), and 3 juveniles of Macropodus spechti (they're about 5 cm)...
I read something about keeping them in ponds on an article on "Der Makropode", where was specified that it's important for temperature not to drop below 15°C...but I also read (this time on an Italian article) that they were mantained all time at minimum 25°C...
What about your experience?
I keep them at 20°C, a little above room temperature (18-19°C during the day, 15°C at night)...

Then, what about water chemistry?
I use 50% RO water and 50% tap water, a mix that gives me pH 7,2 kH 8 and GH 10...it's all right or I have to change something?