The author remixed this model.
This is a moss dome to hold down and protect any plants you may have in your aquarium. I added a ring around the bottom edge to make it easier to print without a brim, and easier to remove a brim if you need to use one. I also added a little lip around the ring to help it stay secure in the substrate of your tank.
This is still a bit of a torture test of your printers retraction settings. So some stringing is possible. My settings are pretty good. However I still get some tiny hairs, but after a quick use of my lighter all the tiny hairs have easily disapeared.
I have made this in PLA and PETG without issues. As for how safe they are for your tank. I read on reddit and some other forums that both materials are safe, but still do your own research. As I am not responsible for any damages your particular filaments may cause to your fish/plants.
This is my first model and I hope you like it! Please feel free to ask any questions and post pictures of your results!