Dull looking discus

[Xxredxx]

Hello my name is Holly, I have had my discus for 6 years now. About a year-and-a-half ago I upgraded my 45-gallon hexagon to 120 gallon hexagon with a Sump System. At that time my brother-in-law who is a big fish enthusiastic told me that black sand would really make my discus pop. The black sand made my discus go dark even with my light keep background and my giant piece of Driftwood in the middle of my tank, they stayed dark looking. So two days ago I decided to finally tackle changing out my sand to White. Almost instantly every single one of my discus colored up brightly. Accept my red turquoise discus fish, he's not dark anymore but he's like a shallow color of what he should be. When I had him in the whites and in the 45-gallon he was bright and vibrant, when I put them in a hundred and 20 gallon sump with the back sand he turned dark, then I changed it to the white sand took a very long time to do. He's no longer vibrant he's now like a shallow color of his former self he's not dark he just looks extremely dull like his red is like orange and his blue is like a yellowish-green now. And Screenshot_20200201-212419_Facebook.jpgScreenshot_20200201-213145_Gallery.jpgmy water parameters are good and I feed them once a day with brine shrimp so they got plenty of food and they have tons of space I just don't know why he didn't perk back up like the other discus. Will it take time for him for his color to come back or could there be an underlying cause to why he still a Dulles color of his former self.

[peewee1]

You know that the fish tend to blend to the shades of light and dark of their environment. A bright background, white or now sand, or bare tank. The color foods can turn the red more red. Al's bio freeze dried black worms and the Tetra bio color foods.

[Willie]

I paint all three sides and the bottom of my tanks a light blue. It works with just about every discus color.

Willie