Fishs are not contrary to mammals and birds warm breeders, but change-warm animals. Their organism adapts to the water temperature in the aquarium. The vital functions, like e.g. the fodder admission and the metabolism, sink with falling temperatures. We must offer our aquarium inhabitants thus to them the affirmative temperature in their area of life.

In the aquarium we can offer stable conditions of temperature to the fish. An automatic controller provides for always constant temperatures. The often spread opinion, which must itself adapt temperature to the dailytemporal rhythm not to maintain is. Fish, which lived as can be prove 10, even 20 years in the aquarium, are proof for it. These fish would have substantially smaller life chances in nature.