Sorry for the poor photo quality - the weather has been bad all day.
First, draw the bottom of the tank. Color it to resemble gravel.
Next, draw what you want in the tank. I put in colorful fish, seaweed, and a treasure chest. Some more ideas for your tank - a hermit crab, starfish, seashells.
Tape the tank contents to the wall, and tape it to the bottom of the tank.
Put it on your shelf and pretend you're looking into the ocean. It might not be the real thing, but it's close enough.
What's your favorite way to beat the heat?