I designed these floating rings to help create holes for light to go through as the surface of my aquarium is covered in floating live plants. This is a good way to see in, let light through and creates a spot to feed the fish. I have made the rings at 20cm, 15cm, 10cm and 6cm. Original files have 1.8mm holes around the edge that will fit a scrap piece of filament to make chains. 

Edit** Upon request there are now versions without holes to decrease chances of it not being water tight.

Hope this is useful to other enthusiasts!

Print instructions

Rafts:
No

Supports:
No

Resolution:
0.3

Infill:
0-5%

Filament Material:
PETG

Notes:
Easy print, use no infill if possible. This keeps it light weight and fills the cavity with the most air possible.