How to make the background Pitch Black like this?

This is an ad from Waterbox. Also in many other tanks I've seen they have a pitch black background, meaning little to no light reflection on it. In my 75gal tank I struggle to do that. My Kessil lights always spill some lights on the background.

How to make intelliJ thematically similar to chatGPT? (pitch black background, same colors for classes and variables etc.) : r/IntelliJIDEA

Pitch Black: A Dusklight Story - Episode One on Steam

Pitchblack Playback

Water Flow in the Dark, This image was pitch black on my ca…

2,228 Pitch Black Photos, Pictures And Background Images For Free Download - Pngtree

Here's How to Shoot Portraits With a Black Background - Peerspace

Pitch Black Pictures Download Free Images on Unsplash

Pitch Black by Axel, Shaquille Griffin, Justin Jusino, Anna Branch, Connor Wardell

Pitch Black (film) - Wikipedia

Black background - Imgflip

26,631 Pitch Black Backgrounds Images, Stock Photos, 3D objects, & Vectors

How to turn on dark mode everywhere

Image tagged in stop scrolling arnold,black background - Imgflip

How to make the background Pitch Black like this?