If you don't have a top, your fairy wrasses will jump out. I lost a Lineatus that jumped out 10 seconds after I pulled one of my screen tops to the side to feed. Unfortunately the position I was in, I was only able to see the fish launch out of the corner of my eye, and I freakin' couldn't find it. After looking all over, I assumed it went behind the tank where I couldn't see or retrieve it (I'm in a wheelchair and the layout of my tank room and my 6' tank don't allow me much access behind the tank). I found the fish a week later in my controller cabinet... a place I had looked... but the path and distance to enter the cabinet were so improbable, I didn't put much effort in searching the cabinet.
Since I lost that fish, my remaining two fairy wrasses have been picking at each other and often launch themselves into my screen tops. I doubt I could go a day without one of them jumping out if I had no tops.
