Thank you very much zozo - absolutely wonderful details of your open tank Why I can't have an open tank , too? Main reason: I am running out of time and at the moment I really do not want to open another construction site ... But I am thinking about my big 650 l tank - its lids are quite damaged in the meantime anyway and the light is laying extra from the lids on the tank, too- I am afraid soon I have to try it open ... but 650 l loose a lot of humidity to the living room. Hm? Hm? Hm? Hm?