Warm white fluorescent
The flickering light over the small aquarium is now fixed, it was the fluorescent.
(the filter is of cause also cleaned and working as it should)
The only thing is that the easiest and quickest fluorescent i got a hold of was a warm white one and that is not the nicest light to have in a aquarium, everything is yellowish.
Edit: I think It looks quite OK even though it has been whiteout light for about two weeks (it is placed in the middle of our apartment so it will not have any light from the windows either).
