I designed this for my new betta fish, the sainsmart tpu really glows under normal lighting which is great. I designed this to fit my $12 Walmart 1 gallon tank. The trick is to print the green tpu on the first two layers, pause the print, and swap to the black pla for remaining layers.

Tank used:
https://www.walmart.com/ip/Aqua-Culture-1-Gallon-Aquarium-Starter-Kit-with-LED/33874882

filament used:
https://www.amazon.com/gp/product/B00TI3JUSI/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

https://www.amazon.com/3D-Printing-Filament-Dimensional-Accuracy/dp/B01MUBEAD9/ref=sr_1_3?keywords=3d+mars+black+pla&qid=1555013052&s=industrial&sr=1-3