Plastic canvas is the greatest thing since sliced bread! It is so useful in the aquarium. I used a sheet of it once as a makeshift divider, worked like a charm! and it collected algae for a fish snack

You can also use it to make small hidey holes for your fish. Someone on this forum made a cave and put leaves on it. The fish loved it!
I have found platic canvas balls to be useful too. I have an extra one in every tank that has some cycled media in it. it just floats along like a beach ball and helps me to see the current in the tank. The media gets used when I feel like changing a filter, I already have a clean piece that is seeded and ready to go. The fish don't mind it and when it gets algae on it, they have a floating snackbar.

it looks like a disco ball
Everybody should show off their plastic canvas creations, I bet there are alot of good ideas out there!