[j_man]

I have heard of people who don't do water changes.So I have some questions. Wouldn't not doing water changes eventually "wear out" the water? Scientifically speaking everything breaksdown into something, until it is just basic organics. So wouldn't old water eventually saturate or breakdown?

[Steven Pro]

There are always people that go for a year or even several without doing water changes, but eventually things go bad real quick and they are not able to recover.

[Reefland]

In a nutshell, yes things will eventually accumulate to the point of no return. Best practice is to perform water changes frequently.

[Ninong]

Water changes are a good thing for lots of reasons. One reason that many people overlook is that water changes help prevent or reduce the build up of certain organics and trace elements that might otherwise reach harmful levels.

A 15-20% water change every four months is probably a minimum for most reef aquaria but most people do them every six weeks or so. I know of some people who do as little as 10% once a year but that's pushing it. If I were to make a general recommendation to someone just starting out, I would say that they should do a 15% water change every 4-6 weeks. Another approach would be to do a 10% water change every 3-4 weeks. I don't think there is any need to do more than a 20% water change in a reef tank unless you have an emergency situation.

Yes, some people say that they have been running for years without a single water change but that's probably not the best approach for several reasons.