Just wanted to underscore what Scott said. The bacteria can only exist at levels equal to the nutrient source. One fish in a large tank would only be able to sustain a certain amount of bacteria, regardless of the filter surface area, flow rate, oxygen levels etc. Having a fast turnover does not necessarily mean the filter is removing more waste. Sometimes the flow can be too fast for the bacteria to be effective. ------------------------------------------------------------------------- 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"!