Water changes?

[skip_16157]

Can someone explain to me the importance of water changes? I have not done one in three weeks and my water chemistry is perfect (A=0, N=0, Ntrite=0, ph=8.2)

The book that I read said to do a 5% biweekly change. I am not oppossed to do these changes just want to understand them more. I have no corals but will probably get some once I get new lights.

How do you know when your due for a change?

 

[loganj]

Two things come to mind here. One: There may be a buildup of undesirable compounds in the water that will not register on water tests. I imagine a good skimmer would keep most of these under control though. Two: It's a good way to replenish trace elements. Both fish and inverts need certain trace elements to stay healthy. You can dose this stuff of course and probably keep it within reasonable parameters. I do water changes on my tank and everything seems to perk up some afterwards. I know there are people who have kept tanks without changing water, but I think it's a good idea to do it. JMHO.
Logan J