Black background for back of tank

okay so today I put a black background one the back of my tank and also on one of the smaller sides that faces a wall. (in other words the corner) and now my fish seem unhappy -- is this a bad sign? should I remove background or will they adjust?

Premium Photo Back view of young woman in black tank top looking down on black backgroundgenerative ai

Addition of a black background. Fish tank, Tropical fish aquarium, Aquarium fish tank

.com : N4L Aquarium Background Black/Blue Double Sided Decoration for Fish Tank (48 L x 24 H) : Pet Supplies

Shades of Aquarium Style: Exploring Black and White Background Options - PetHelpful

Black background for back of tank

Black Rock / HD Stone Aquarium Background Rocky Fish Tank Background - Sweden

black background Aquascape, Aquarium decorations, Fish tank

180,330 Black Tank Royalty-Free Images, Stock Photos & Pictures

3D Effect Black Stone Texture Aquarium Background Poster Fish Tank Backdrop Deco

49,497 Tank Top Isolated Images, Stock Photos, 3D objects, & Vectors

Powerful Military Tank - Dark Gray Black Color - Back Side View Stock Illustration - Illustration of cannon, turret: 275959225