Nitrite of 0.5 ppm is not that significant. I'd be willing to bet it was the chlorine levels in a large volume water change without treatment for chlorine. If you want to deal with the nitrite and ammonia, add some plants. Bob Dixon ------------------------------------------------------------------------- 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"!