Well my friends, just to give you the last update:
This story have a sad ending. I found the yuvie albino socolofi dead 15 min ago. It happened almost after 42 hours of fasting period and same time since I noticed him with fast breathing for the very first time.
Now, I have some questions and feel really concerned:
1) Can constipation kill a fish that fast?
2) Could it be something else; as bloat?
3) Should I then treat the whole tank now with Metronidazole or should I wait to see if another fish appears with the same symptoms?
I have lost 2 fishes now with these symptoms and don't want to loose another one in this way. Please, help me answering my questions.
By the way, thanks a lot for your help and for your replies to this thread!!!