What about taller growing plants put at the back of the tank that will eventually reach the surface and sort of sparwl across the surface? Plants like, Elodea, Ambulia, Cabomba, Myriophyllum (common name Parrot's feather), or even a small type of water lily such as Banana Lily, these all spring to mind for creating living shade for the glass catfish. If water hyacinth is allowed where you are it can be a great plant in an open top tank, with plenty of light it should even flower but it might get a bit too wild and quickly cover the entire surface area. The fish will also really enjoy hiding in amongst its dangling roots.
I currently have Elodea, Ambulia and Parrot's feather growing in may tanks and when ever it gets too wild across the surface I just trim it and replant the ends or if there is too much I put it on my gardens or in my compost bins.
