I have a gorgeous corner tank made out of acrylic. The back acrylic pieces are solid blue in color. They are not transparent at all. I need ideas on how to change the background color to black. Is there a safe paint that will work inside of the aquarium?? I thought about using plastic backgrounds or plastic sheets but I have a small opening which means if the plastic is stiff, I will have to cut it into multiple pieces and this will show distinct lines on the back of the aquarium. Any ideas from you DIY people?