Does keeping fish in an opaque container stress it out more than in glass tanks? I have a huge china pot (looks like those for plants) and I want to set up an exotic Japanese kind of lily + fish 'pond'. The inner wall is brown. I tested buy putting some small sized guppy, gold fish and sucker in it, but they seem to adapt poorly compared to transfer to new glass tank, they always swim at the wall, head against the wall. Anyone with experience in this please? Thanks!