Where can i find a lid for

[TheKid]

Could an eel pass through egg crate?

[rayjay]

Putting a glass lid on a salt water tank greatly inhibits the necessary gas exchange that takes place at the waters surface.
Egg crate or screen is a much better method, with egg crate being the one to allow better air and light access to the tank.

[saltwaterseahorses]

mk i see now!