The strong fiberglass reenforced weed cloth could be sewn into a tube. The bottom sewn shut as well.
Then the tube is hung and filled with Perlite.
Small holes can then be cut where you wish to insert plants.
Water dripping from above keeps the vertical garden moist and a tub at the bottom collects the excess to be returned to the fish tank, or better yet just hang the tubes over the fish tank!
The cost would be extremely low.
Next best idea is to use Solid Drain Field pipe.
Here's my contractor prices in California for pipe.
4" Sch 40 - $2.12
4" class 200 - $1.95
4" Drain Field - $0.74
6" Sch 40 - $3.68
6" Class 200 - $4.33
6" Drain Field - $2.48
Traditionally the vertical tubes havebeen made of PVC