Fish Are Invisible With Natural Substrate

I have 9 Tiger Barbs.
I have natural river gravel substrate.
The Barbs are almost invisible against the rocks and substrate.
The substrate needs to be a darker color. A mix of my current substrate or a Complete color change?
Can I mix a darker gravel with natural stone gravel or should I change to black?
Or another dark color.
Thanks in Advance .......John

 

You can mix different color gravel or add some pool filter sand to some areas. Be sure to rinse whatever you decide to add.

 

I don’t want to introduce sand.
But there needs to be a contrast from the fish and the surroundings.
I’m leaning to a solid color.

 

Then I think going with black would make the barbs stand out great

 

Darker substrate will bring out fish's colors more. Light substrate will cause them to "bleach" themselves. So if you can, go for black gravel

 

Do you have plants? I like natural gravel and with plants the fish do stand out in my opinion.

 

No plants. Just natural rocks and gravel.