Definitely get a lid. There are tons of fish that are notorious jumpers, and even those that aren’t known for it will jump from time to time. Funny story about jumpers (well sort of). Back in my freshwater days, I had an American Eel, and besides an Undulated Trigger I used have, it was absolutely the most aggressive, nasty. and just plain mean fish I’ve ever had.
Anyway, I would usually feed him every other day (it would only eat live fish or shrimp), and he was always ravenous, the fish and shrimp I’d feed him would never last more than 30 seconds, and one day he didn’t come out to eat, so I left the goldfish in the tank thinking he’d eat it later. 2 more days passed and the goldfish was still alive, so I knew something must be wrong.
So, dug through all the gravel, tested the water, etc, he was gone. I figured he either got out through the hole in the lid for the filter or he just died and quickly decomposed. TBH I was kinda relieved because he was mean, couldn’t have any tank mates and it was a ***** to have to feed him live food.
The next day, my dog comes and drops what I though was a stick in front of me, and I pick it up and it’s the eel. His skin was like leather and he was covered in debris, but he was ALIVE!! After at least FOUR days!!! I put him back in his tank (and covered the hole in the lid) and he just laid there motionless (but gasping). I came back a few hours and he was gone again, but so was the goldfish.
I had him for another three years. And then gave him to a friend, who later was in an accident and was in the hospital for months. The power at his house was shut off for days, they called me to come and deal with his fish tanks. It was November in Idaho, so everything was dead. Except for that dang eel!! The water in his tank was probably 45°! For days! And yet he endured!!
By far the most bulletproof fish I’ve ever seen.