I will probably get a certain amount of backlash from this suggestion, but I would get a piece of flexiglas mirror (I think that is a trade name) cut to fit that end. Its plexiglass and light weight and if it is cut properly the bottom can rest on the frame and you can tape the top inconspicuously to the top frame. I cut it myself with a scroll saw, (but should you do that don't put masking tape on the back side to run the saw on - you will pull the backing off the mirror when removing) I have used the mirror on two of my tanks and have not had any problems with fish being obsessed as some warned. I have bettas and angels in the tanks (besides other community fish). I would actually use it on all my tanks because it effectively hides all the wires, etc. but I have no more left. (Angels are the only cichlids I have)