Douro How to raise a blue bottom, God call for help! Welcome to discuss

This is the appearance that the white background has just entered the black background. It took three months to get home. I bought it back with a light green background. How can the blue-green background be deeper? Today, I asked the senior fish merchant to tell me that basically do not turn on the lights, black background and black back tank. I have read a lot of related articles. I really don't know how to raise them. Help!

Douro BayciTR comments: it takes time to precipitate the fish when the background is still small.

Youyuxinjing comment: happy National Day holiday, everyone! Top up the post