Rather than going for one of the $15US backdrops available in the LFS here, I opted for a less expensive, yet still effective solution! I spent 99 cents at a local drug store and bought a blue posterboard. I also bought a black one. I cut both to fit the back of the aquarium, and then had the family vote on which color they liked better. We ended up going with blue.
Aquarium before backdrop:
Aquarium with posterboard backdrop:
The camera flash actually made the backdrop brighter than it is under just the aquarium lighting.
I'd be interested to see more backdrop ideas from forum members.
Aquarium before backdrop:

Aquarium with posterboard backdrop:

The camera flash actually made the backdrop brighter than it is under just the aquarium lighting.
I'd be interested to see more backdrop ideas from forum members.