Danio Question

[-ED]

I changed my water in my 55gal yesterday and today I've noticed that all of
the zebra danios have been poised in a static position near the surface,
just staring at the hornwort thats floating in the corner. I mean..they're
just static.as if they were watching to see what's in the hornwort. They've
been like this practically all day today. They took to the flake food, then
back towards the hornwort. This is most peculiar. Does anyone have a clue
to this behavior in danios ?

Thanks -ED