I've been debating on a cover but I think I'll end up getting one to cut down on evaporation and avoid accidental fishy suicides. Not sure if I'll end up with any stock that's prone to jumping, but there's always a chance from what I've read.
And also because I have cats. I can just see one of them jumping to the top without realizing that there is no top.
I think if I had a cat, I'd be sportin' the cover too! Maybe it's all the cartoons when I was a kid...