Single-shot containers

My initial intent was to create open-volume containers of appx 4 sqft, but I've since realized that these are potentially problematic for some experiments, such as root crops, because they allow root networks to intermingle, so I need to be able to isolate the individual growing volumes.

So in addition to the larger Kratky research tubs I'm organizing, I may also need smaller, single-plant containers for more focused experiments. I’d like to be able to build these to my own specifications for testing, using my 3D printer, so I can adapt and evolve the design as my needs (and experience) evolve. I know this is doable, but my initial test was a failure. I printed a 50mm cube canister in PLA, with standard print settings, filled it with water, and set it on a piece of tissue (Kleenex), thinking that if it leaked at all, the tissue would reveal the leak.

Well, it has been 4 days now and I just discovered that all the water is gone, but there was never any moisture visible on the container’s outer walls or distortions of the tissue. Upon closer inspection, however, the tissue has stiffened and developed a subtle watermark texture that wasn't evident in my earlier, more cursory inspections. It seems it didn't so much leak as osmose straight through the walls of the container.

I'm going to try again, but this time I'll be using PETG filament, and changing the print settings to hopefully eliminate the osmotic pathways.