Why are my fishes jumping?

I have a hood on my 5g tank but it has a hole in it because of the heater and filter. The holes a bit too big so there's enough room for a tetra to jump out. i have 5 tetras. i started with 2 but 1 jumped out and died. Now when i turned off my light, it's pretty dark you can't see the fishes. I heard a water splash and saw the orange stripe of one of my fishes really up high of the tank. I'm not sure if it was jumping though. I turned on the light and my 5 tetras are still there and alive. I would say it was luck because it jumped out on the wrong side.