I not only cover the tank, I also cover the overflow box. I just cut a acrylic piece to put on top of the overflow box, under then tank cover. Mt tank is escape proof. Last time i loose the fish due to jumping was when my beautiful Naoko Male jumped when I remove the lid quickly to dump in food in the AM. I was in too much of ha hurry to notice. I am taking about cracking up the lid and dump food in, 3-5 seconds at the most. I get to the point I just dump food through the top screen instead of open it up.My flasher somehow got down into my sump last night. Probably be dead had I not removed the filter sponge. Managed to catch it and put it back but immediately jumped and hit the floor tiles. Looking quite rough. Hopefully it will survive.