This is a custom made isolation tank for the Ciano Aqua 30 fish tank. The isolation tank itself has holes of 4mm in diameter, which is small enough to that it stops my guppies and tetras being able to pass through it whilst also providing decent enough size holes so you can see though the sides.

The isolation tank doesn't hook over the edge, but rather rests on the brim under the lid and hooks over the two squares which we don't use in our tank. The lid of the tank will still close albeit doesn't sit entirely properly.

I used Elegoo transparrent PLA and with a 0.8 nozzle, although it also prints fine with other nozzles.

Supports are required. Note there are no holes on the sides with supports to prevent sharp parts or bits of plastic being left behind.  Be careful when removing the supports because they are supporting thin bits of print.