Here is a simple two part lid for a standard 2.5 us gallon aquarium. should fit any of the ones you would buy at petsmart/petco/walmart. if you have a critter that can climb and push out i would recommend you devise some sort of securing mechanism. works great for my emperor scorpion, keeps the cat from messing with it.
.40 extrusion width with 0% fill layers: 4 top 2 side 3 bottom. printed in eSun PLA+