What are they doing?

[silverdollar]

I have three silver dollars in my 30 gallon tank and I think they're all males. They do this weird thing. They swim side by side almost touching each other and they shake and shudder while they're swimming.

What are they doing?

 

[smb]

If they're all males they might be sizing each other up. I doubt anything will come of it with Silver Dollars if that is the reason.

Cichlids do this also when another encroaches on ones territory and some do it before breeding.

 

[AquaNut]

My silver dollars do something similar when swimming through the output current from the filter. I've never seen them doing anything even close to territorial or aggressive, though. They're so shy, they cede right of way to air bubbles.