I want to do a terrarium after reading about them on this website. I want to do a terrarium in a 40 gallon long tank and put my venus fly traps I have in there.

Do you always need a top on top of a terrarium if you do it in an aquarium? I didn't see anything about this?

Depends if you want high humidity or not. With no top humidity wont be high. But if all thats growing in there is flytraps no top would be ok because flytraps dont need that high of a humidty. Are you growing any other plants in it?

i'm moving this to carnivorous plants!