I love the tank man. Just started made my 20H planted with Amazon Sword and Hornwort. I went with the black sand too but I think you just inspired me to paint the back black. Can you tell me what kind of paint you used.
I just used a flat black spray paint from Lowe's. 99% sure it was Valspar. Any flat black spray pain should work. Just make sure you tape off every single other side of the tank otherwise you'll get some mist on it