I have an idea for a direct marketing product. Take a regular accessory for fish tanks, A piece of coral, a plastic plant, even a treasure chest. Split the item down the middle vertically. Attach magnets along the split and cover it with felt. Attach the two together, one inside the glass, and the other outside the tank. It could be marketed as a way to make your 2D fish tank pop out into the real world! instead of a boring flat surface, you can now make your fish tank part of your world! Enhance the beauty of your fish tank while giving your pets a place to live! Place this simple accessory on your tank and both you and your fish can enjoy the hard work that you put into creating a work of art!. It also doubles as a handy fish tank cleaner!
Sell them in assorted sets of 5-10 pieces. include a plant, a coral, a chest and some other items. The package would probably cost $10. After the pitch, double the offer and give free shipping (extra S&H on the free set)