I am pretty sure the oily film I get in my tanks (and probably you get in yours) is indeed "protein scum", which is why airstone/surface agitation helps get rid of it. As Kaycy sort of mentioned also, I didn't start seeing this film until I began mixing crushed flake food in with frozen bloodworms. I get rid of it by simply sucking it off the top when I do water changes. -Doug Brown debrown@kodak.com ------------------------------------------------------------------------- This is the apistogramma mailing list, apisto@majordomo.pobox.com. For instructions on how to subscribe or unsubscribe or get help, email apisto-request@majordomo.pobox.com. Search http://altavista.digital.com for "Apistogramma Mailing List Archives"!