Water The water is going to be no help. The bacteria is on and in the solids(sand and rock) Use all new water if you can. There are bound to be more of something you don't want (No3) and less of something you do want (trace elements) in the old water. I upgraded from a 135 to a 220 and was scared to use too much of the old sand because of stirring it up and releasing bacteria in the new system. I just added a small amount of the old sand to the new system to help seed it and then used all of the old rock. Next all new water went in. The system has been up for a year now and doiong very well. Just my 2cents
Scott |