<I noticed some black particules on the tank of the membrane (like carbon I <would guess) <Could it be coming from the carbon prefilter ? <To be sure, I exchanged the pre-filters order, so now I have: carbon, <sediment, membrane. I am by no means an expert on filtration but, I would venture to say that you will prematurely clog your carbon block by running it before the sediment filter. My suggestion would be adding another sediment after the carbon block to catch any carbon particles that may be dislodging. Although it is possible the black stuff your seeing in the membrane housing is the result of anerobic bacteria. How long does your RO unit sit idle between uses? Tim ------------------------------------------------------------------------- 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. apisto-digest@listbox.com also available. Web archives at http://lists.thekrib.com/apisto Trading at http://blox.dropship.org/mailman/listinfo/apisto_trader