DIY version: http://www.koiphen.com/forums/showthread.php?t=104042
Go through the whole thread. There are links to several versions. As far as I can understand it, yes, the foam is created by the agitation of the falling water (as opposed to injected air as in a traditional skimmer).
Go through the whole thread. There are links to several versions. As far as I can understand it, yes, the foam is created by the agitation of the falling water (as opposed to injected air as in a traditional skimmer).