I got a strong net on top of my 1000 so my fish never get out and it wouldn't injure the fish when they jump! my 2ft spotted gar can jump like 2 ft high!
Started in the fish hobby less than three years ago.
I switched from the 1" mesh net to the 1/2" mesh net in my "Gar"-den pond and all occurance of jump out have completely ceased.
It is very wierd, I had many Gars and Bowfin leap from a "raised" pond, but I have only had one gar jump from a tank though. My very first ever LNG "Logan" jumped when he was under 8" during a water change. It was way under 30 minutes out of the tank. i was able to get him back into the tank in plenty of time.
I released Logan last weekend into my Farm pond with his favorite Florida, and they are still hanging tight! Logan measured 25", The Florida < 14".
With the 250,000 - 500,000 Golden Shiner Minnows I added two weeks ago to the pond, they are loving life.
I rarely ever "cover" the aquariums that I keep my Juvinile gar in, and don't have challenges with them jumping.
Bichirs and Crayfish are an entirely different animal.
I cover the "F" our of the tanks with these, and have had 5 Bichirs manage to esacpe to dry out. The marbles (self Cloning) crayfish do 100X better in an uncovered tank than a covered tank. Only 95% UP AND WALK OUT of the aquariums through no lid covers. I don't think that I have ever in 100,000,000,000 times ever seen a Marbled crayfish not "exit" a "fully sealed?" aquarium.
Lids are nothin to a "crayfish" but a unresistable game. Open lids will allow them to come and go, as long as you leave a ramp so that they can eventually craw back into the tank if they decide.
They are also nothing like fish when they "leave". You always "find" the fish eventually, if nothig else from the gagging smell of the decomposition. I have never found and of the bazillion or so Marbled Crays that may very well still be in the basement somewhere tearing it up.
I'll probably wake up in the middle of the night, being devoured by a bazillion Marbled Crayfish!