Is this a mating behavior?

[gwand]

These two celestial pearl danios have been circling each other and shaking their posteriors. Is this a mating ritual?

Also both fish have developed a yellow “racing stripe” or “tire tread” along their entire dorsal surface. What is that? The other CPDs do not have this alteration.

 

[Back in the fold]

I don’t “think” it’s mating behavior . Danio’s , if these are like Zebras and others , chase each other in groups scattering their eggs as they go . This looks like two males trying to assert dominance . Females don’t generally do that .

 

[seangee]

2 males shaping up for a tiff

 

[Colin_T]

2 males displaying to each other as mentioned by seangee.

The yellow stripe along the back is produced by some male fish and appears when breeding or displaying to another male. Male rainbowfish and Galaxias show it as well but their stripes only go from the nose to the first dorsal fin.