Help with DIY canopy hood warping

[Evofish]

Thanks for all of the advices guys. I will take it into consideration. Although, I had an idea yesterday. I used saran wrap and covered the underside of the hood, this morning...no warps! If this holds up I will incorporate some kind of "wrap" or seal. Or maybe even tiles like someone mentioned. Anyways, here are some pictures.

 

[CHOMPERS]

Since the wrap worked, give the inside a coat(s) of polyurethane as a vapor barrier.

 

[Evofish]

Okay, the saran wrap slowed down the warpage but it did not stop it. The whole thing is coated with min-wax polyurethane clear coat. The next thing I will try is to add vents like Dan Feller said. My last resort is to build another hood but made from plywood like I'm suppose to.

 

[tigermax]

When I built my canopy out of half inch mdf board, I added computer fans to the back. One blowing air in and the other blowing air out of the tank. Never any moisture build up or warping.

 

[CHOMPERS]

If the only warpage that concerns you is in this picture,

then use a pencil to mark an even distance from the piece of trim (be creative in making a spacer) along the entire edge of the warpage. Then dissassemble the hood and use a planer or belt sander (available at any tool rental) to shave or sand the piece down to the marked line. Then just assemble it again with the current pieces in their same locations and orientations.