I see it a lot on my tanks... it is protein "scum"... It is mostly harmless to the fish... Airation, protein skimmers, or overflow based filtration systems will get rid of it... --Cliff ------------------------------------------------------------------------- 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"!