Thanks for all the answers
I`ve been away on tour again so I haven`t been able to respond. Of all the suggestions, I can rule out a couple. One of the very few advantages of living in Norway is that our tap water is probably the cleanest in the world. So there are no issues with water changes and "contamination". For instance, de-chlorinaters are generally regarded as a waste of money over here
The water is soft and quite basic. I don`t overfeed. Quite on the contrary. Even when I`m at home, over longer periods, I feed very little. I currently have 4 Loach tanks up and running. Species are: Skunks, Clowns, Yo-Yo, Histrionica, Kubotai, Kuhlii, and other dithers, like Tetras, Guppy, various Ancistrus, SAE, Scalare, Betta, L239, Cory...(not all in the same tank, of course
) Apart from size. all tanks are pretty much the same when it comes to water-parameters: PH approx. 7 - 7,5. No ,or very few, plants, sand substrate, GH around 2-3 dh.
I`m not advocating rare water changes or anything. I was just curious as to why my beeing away so much seemed to be no problem for my tanks. In regard of water changes and water parameters. I imagine my over-filtration is the main reason. But that doesn`t account for the low nitrates, though?