I have a 240g with 2 narrow openings (approx 16" long x 2.5 wide) and would like to preferably buy a basket-like container to grow out pothos. If nothing like that exists for purchase, is there a DIY?
Egg crate (light grid) would work but take up more space, try Darice plastic canvas mesh from a craft supply store and use fishing line or polyester thread to 'sew' the sides and bottom together to create an open top box.
You can loop a zip tie through the basket holes to the hoses to keep it from falling into the tank.
I second egg crate if you don't mind the white look. Just cut it to size and use zip ties to make the box. You could paint it with black krylon fusion to hide it against the black background.