I picked up a sheet from Lowe's earlier today......got it home and cut out two dividers for two different tanks.I prefer the eggcrate as long as the fish cannot swim through the holes(which would defeat their purpose lol) to the store bought dividers as I suspect that water flow is slowed down due to the tiny holes of the dividers.
I didn't bother asking any workers this time. Bought it online and did store pickup. Especially after asking 3 workers at home Depot and they all couldn't find it. My receipt says Louvered ceiling light panels.