Sump flow bypassing middle section.

[TheEngineer]

There is glass attached to acrylic for the overflow. That picture appears to be the front of the glass though.

 

[Philipgonzales3]

The part I circled is likely not glass. Look at how your glass panels butt up against each other. The black piece is not actually structural, if I’m viewing it correctly. I think Reef Savvy started this feature, though it quickly spread in the industry. I have them on mine too. It helps with things like preventing your algae cleaner from damaging the structural silicone seal.

Ah OK. I think this is just the silicone itself. Appears to be rubbery and not hard plastic when I press it. I think they are just thick silicone seals?

 

[wangspeed]

Oh wow. That is a super wide seal. Not sure what to think about the bubbles then.