>From what I've heard, the surface tension of freshwater is insufficient to maintain a froth - having said that, large scale freshwater protein skimmers are used on large trout ponds here in Australia. The amount of aggitation for a freshwater p/s for a regular tank would have to be quite substantial. Regards, Simon Voorwinde ========================================================= svavev@hunterlink.net.au http://thecichlidtank.cjb.net ========================================================= ------------------------------------------------------------------------- This is the apistogramma mailing list, apisto@listbox.com. For instructions on how to subscribe or unsubscribe or get help, email apisto-request@listbox.com. Search http://altavista.digital.com for "Apistogramma Mailing List Archives"!