I would advise against using acrylic in a glass sump. The quote below is from RocketEngineer on reef central found in this
thread,
"ACRYLITE FF sheet also absorbs water when exposed to high relative humidities resulting in an expansion of the sheet. At relative humidities of 100%, 80% and 60%, the dimensional changes are 0.3%, 0.2% and 0.1 % respectively."
So, think about that for a moment. The vendor of the material claims a 0.3% expansion of the sheet at 100% relative humidity (a.k.a. immersion). That means for a baffle 10" long, that sheet will expand 0.030" Or ~1/32".
Now, lets figure out what kind of force that would cause:
Y=(F*L)/(A*DeltaL) where:
Y=Young's Modulus (400,000psi for acrylic)
F=Force (lbs)
L= Length (baffle length = 10")
A = Area (Assume 10"X 0.25")
DeltaL = Change in length (0.030")
Rework the equation:
F = (Y*A*DeltaL)/L = 3000#s
That's right. 1.5 TONS of force are pushing on the inside surface of that pane of glass due to expansion of the acrylic.......... And its right in the middle of the glass along a very narrow region.
The moral of the story is don't mix materials when the ends are constrained."