Are They Doing A Spawning Ritual?

[Meeresstille]

Hello All,
Tonight I fed the fish some frozen bloodworms again, they get those about 3 times a week. I was then spending some time watching the tank after the feeding, and noticed two of the Harlequin Rasboras swimming, or rather hovering beside each other wriggling or shaking and shimmying against each other. At first my heart dropped thinking they may be flashing, it being a sign of ich or another irritant. 
 
But as I kept watching it looked like they were searching each other out and not "flashing" at anything but each other. Then one swam off and the other started chasing some of the other Harlequins or trying to do the wriggling with others still.
 
Do you think it may be a spawning ritual? I googled this behaviour and some hits say that they may be fighting, but it does not look like a form of aggression to me!

 

[ncguppy830]

well i highly doubt that, they are very difficult to breed and require very soft water so most likely there fighting and trying to set a pecking order.

 

[Meeresstille]

Hmm, weird! I had them for a few months already...well, whatever it was they've stopped doing it!

 

[Lateral Line]

Harlequins spawn, "upside down" under an overhanging leaf of an aquatic plant, they are not typical egg scatterers. As mentioned above, they require very soft acidic water. What you describe is not typical spawning behaviour for the species.

 

[Meeresstille]

Thank you so much for the info.  They've stopped the behaviour since then! But my city's water is very soft and the pH from the tap is around 6.5. 

 

[nortonmad213]

just a display of dominance,
just establishing a pecking order.

 

[Meeresstille]

Thanks, Norton. I'm glad then that they've sorted it out!  

 

[GRD1985]

Agreed many fish use the side by side shaking as a type of competition. You will likely see it often or occasionally depending on the species and its nothing to be concerned about.

 

[BelldandyShanny]

I've just noticed this behavior in my scissortails, I'm quite perplexed because they seem to be doing it to my male guppy...