OscarMeyer 280g

[Scythanith]

That happens when the piece of acrylic is either too large and expands in the tank, but its edges are pushing against the glass so it buckles in the middle OR the material just warps lol.

Nothing you can do about it. I'd say pull it out, make new teeth that mount higher up and just use tint on the back of the tank (outside). It will be much easier to keep clear of coralline algae.