Intermediate note:
Well, interesting replies. In summary I’ve got the impression that most of you are good followers of the norms you imposed yourself.
If this is right, the main explanation is the number of tanks to be cared for. If I had only three or five of them, oh, I think all would be OK. But there are 33 small 12-liter-tanks waiting for water change. So, I experience myself as more or less idle and careless. Sometimes, not permanently, fortunately.
The problem is: Fish mostly stand it. There is a reduction of spawnings, of course, but nothing really bad. I even take it to help the fish with conditions of lesser challenging them to spawn, from time to time. But I guess that I am wrong in many cases. Instead, they are challenged by deteriorating environmental conditions. The problem is that they for long periods don’t react with illness or even worser things; so I think: OK, let’s wait with changing water a further week. But this probably is wrong. I know it and I don’t behave better, nevertheless. At least sometimes.
Well, I think: With many tanks you either need (1) help or (2) technical means to facilitate water change. Prepared water with the right values stored for direct usage is not enough for that purpose. No, I mean water drain pipes from every single tank and water change pipes towards it.
Or reduce the number of species/tanks. This I meant by my wish to be frank. Let’s wait for the next postings.