My last tank was an open top tank.
Never had any suicides or problems, you do need to be aware that water loss due to evaporation is greater.
My tank was 60"x18"x22" with a gap of about 4" from water surface to the rim of the tank, there was a 2" glass brace running around the inside so I guess that may have helped a little but I didn't even run cover glasses.
Plants grew up out of the water adding to the display.
Oddly enough the only time I ever found a fish had escaped any of my tanks was when I had a 30"x12"x15" with a hood and cover glasses and an ancistrus managed to find his way out, unfortunately I found him too late. The only thing I can think is he managed to sucker his way up to one of the holes for filter tubes etc.