I'm trying out this idea for tank dividers. I have no clue if it will work but here is what I did.
I found these things called plastic U clips in the office section at walmart. Then I got some little suction cups for airlines at petco along with some aquarium sealant. I cut the part that holds the airline off the suction cup and the glued the u clips to them with the sealant. The tank divider can then slide into the U clips and be stuck to the aquarium. For something more permenent you could glue the U clips to the glass.