Plug for Juvel aquarium

My Juvel aquarium has 2 openings at the back of the lid to feed cables and hoses into the aquarium. However, one of the openings is not needed and I wanted to prevent a snail from accidentally crawling out of the aquarium through the opening. Please do not expect a work of design art. I simply drew the model for myself. But maybe it can be useful to someone else as well. One model has a small opening to lead a cable into the aquarium, the other model has no opening at all.