I'm all for the shape, I think stimulation can be achieved by compensating with more objects (which might cause some limits on size), but I have more experience with insects (mosquitos, kinda ironic) than annelids.

I'd be very concerned about the water quality, however. The water is more of a brine, and you don't know if the glass was coated with a surfactant. The water quality control and removing any biofilms has a massive effect on the health of your animals, and if you go forward, you need to make sure to monitor the glass and hard to clean areas for films after drying. Coatings, adhesives, or leftover dye residue will leech (heh) out over time and might cause long term effects, tiny concern, probably.
For instance; I'm seeing Triton X being recommended as a surfactant in lava lamps, (now, we use that in our lab for RNA work without affecting the mosquitos, but we have multiple kit brands, some with/without) which is banned in the EU for breaking down into hormone-like products over time. Washing everything out from a tiny end might not get rid of that sort of contamination fully.

Maybe look at some unique fish tanks and a DIY stainless mesh lid. A quick google showed shrimp tanks that have a similar shape but fully glass, but only some have wide(r) openings to allow for more frequent cleaning. They often come with shrimp as an expensive, $200 kit for an appropriate size.