I does look like a crack but I think it's just the outer edge of the oil stain, I have members Plenums sent to me fairly regular and Never had one cracked or damaged in anyway But I have had some with staining here
I think your gonna need a bigger pond
The Fraser river down the road from me has Sturgeon in . . .
Yep you are gonna need a bigger pond!!
This on my hit list a weeks fishing on the Fraser after these