Won a 4 foot tall wine glass as a fish tank and wanted to hide the sponge filter but also be able to remove it and rinse it out as needed.
See side build here
Set up the stones and liked it except there wasn't a place for the sponge filter I had forgotten.
The plastic in the container is very stiff yet flexible. Used a box knife for the bottom cut because it was thicker and used a scissor for the top cut.
Then removed substrate and fit in the container part as the space holder.
Now I can just lift it up and out for a rinse and slide it back in quickly.
Circulation seems to work fine as the tank was very cloudy the day I set it up and the next day nice and crystal clear.
Initially wanted to keep the bottom of the container intact but because of the curve of the glass could not. I would have drilled a few holes in the bottom.