I have one last question about Dwarf African Frogs.?

I promise this is the last aquarium question today! ; - ) I have set up a 20 gallon river tank ecosystem. ( With several of you guys helping!) If you've not seen one before, they consist of a 20 gallon tank with a large backdrop built in. The backdrop contains ledges, plants, pools, and waterfalls. This is my question. I added three dwarf African frogs to the tank. They will obviously be able to climb on the backdrop area. There is a 1/8 to 1/4 in gap where the aquarium hood meets the tank due to cords. Is this a large enough gap for the frogs to escape - or do these aquatic frogs even do that sort of thing? I know that fire bellied toads are escape artists from terrariums but am not sure about these frogs. Any ideas?