The make is made of 6 panels, 3 wide by 2 tall for a final product of 24 inches wide by 16 inches tall

This uses an improved panel system as compared to my previous background ( https://www.thingiverse.com/thing:3509102 ).

A double sided aquarium background made of 18 different ~20 cm^2 panels. The maximum size (using all 18 panels without resizing) of the background is 4 feet (1.2m) wide X 2 feet (0.6m) tall.

Print as many panels as you need to fit your aquarium, they are organized by layer (1 being the bottom) and position ("b" goes to the right of "a"). Make sure to get the exact measurement of your aquarium/terrarium before printing to cut down on work and use your slicer to "slice" off any excess length/height from the final row and column panels (note, each panel has been rotated 90 degrees clockwise to allow printing without supports).

Printing is easy and support free, and the alignment of panels is made easy with the inclusion of woodworking style "biscuits". Gluing the panels together can still be somewhat challenging but using the CA glue and baking soda trick detailed in the linked video makes it manageable (watch: https://www.youtube.com/watch?v=Z9qqEbPxx0k for details on the technique [not my video]).

Side 1: sharp detail canyon wall
Side 2: a rounded "negative" of side one, works as an earthen wall.

Designed with 3mm walls and meant to be printed with 20-100% infill and no supports; thin walls in design make the object unsuitable for significant re-sizing (anything less than a 50% change should work).

PLA and PETG are both denser than freshwater so 100% infill will naturally sink to the bottom of the tank.

On safety and longevity:

Both PLA and PETG plastics are generally considered food safe but some of the dyes and additives might not be, so I use "natural" colour to be safe.

The decorations are painted with non toxic acrylics and coated with plasti-dip (also generally considered aquarium safe) to seal the paint.

I recommend printing in PETG long term since PLA is biodegradable and the presence of heat and water will cause it to break down (though from all accounts I've read, it will still last for over a year).

Disclaimer: I'm a hobbyist, and everything I've stated is based on personal experience and google search results; I recommend doing your own research and consulting professionals whenever possible.