Whoops, that doesn't seem to be it. Okay, I recorded my settings:
-Alga Minimalis-Starting pop. 1, disable reproduction, no min. pop., 10000nrg/cycle
-Attached version of Spiral, modified to form swarms
-Small size map (1 or 2)
-No mutations
-F1 costs give the best results, no costs will make larger swarms but take longer to form.