What material for blocking back of canopy?

[jfritz42]

Hi all,

I recently purchased a used 55 gallon aquarium with a nice wood canopy. The problem, though, is that the back of the canopy is wide open and there's about a 4" vertical gap from the top of the tank to the top of the canopy. This is just begging for fish to jump out.

What recommendations are there for blocking up this gap in the back of the canopy? I was thinking of using window screen mesh because this is weather proof (won't rust) and will allow air to pass through so the lights can let off heat.

Any suggestions are greatly appreciated!
Thanks,
Jason