There's not much out there commercially in terms of Christmas decorations for aquariums, but no matter. With a little ingenuity, you can still make your fish tank festive. Here are some ideas.
Change Your Aquarium Gravel to Red and Green
While not explicitly sold as holiday decor, red and green aquarium pebbles are easy to find and can help set a festive mood.
Nature Aquarium polished glass gravel, for instance, is available in both colors from Amazon.
Make a Wrapping Paper Backdrop
Since aquariums are transparent, you could simply choose a nice gift wrapping paper and tape it to the back of the tank.
Now, you have a Christmas-themed backdrop for your fish to swim against!
Use Your Existing Decorations in the Tank
Glass Christmas ornaments and ceramic nativity figures can be placed inside your aquarium.
Just make sure the material you put in your tank are safe for your fish. You want to avoid glitter, glue, older ornaments with lead paint, and anything else questionable.
Experiment with these ideas and you're sure to put together a beautiful Christmas-themed fish habitat just in time for the holidays.
Decorating ideas from: eHow