Hi there
@Wolfw28 ! I was nervous so I used this mesh (4 Pieces Plastic Mesh Sheets for Embroidery Black Mesh Fish Tank Divider Screen Craft Mesh 10 Pieces Binding Bars Sliding Bars for Embroidery Crafting Knit and Crochet Projects
https://a.co/d/c61DQni) to cover the return grates and the top of the overflow (just superglued it right on), but really I probably only needed it for the top given his size when I got him. After he got comfortable with me he started occasionally hanging out at the surface “upside down” and I when I first saw his beak, it was clearly bigger than the Red Sea overflow “grates”, let alone the mesh I bought (but the top open part could have otherwise been a problem). So you could definitely use this, and you may not need it, but you won’t know til you get the octo and see how big it is (and eventually you’ll see the beak and then know for sure). Mine was full grown when I got him so you can get a sense in the video. I also originally used mesh (actual mesh, like fish net mesh) over the return valve, but I stopped because it messed with the flow and I never once saw him anywhere near the return valve.
