Here is a good article to read about water.

http://reefkeeping.com/issues/2005-10/rhf/index.php

"The normally encountered differences in calcium, magnesium, alkalinity, nitrate, phosphate, silica, pH, etc., are unlikely to unduly stress organisms during water changes up to 30-50% using natural seawater or aerated artificial seawater, in my opinion."

In this article it says up to 50%. You do need to be aware of water temp and a few other things, but I'm still not convinced that a fish/coral living in a toilet that needs flushing, is better than flushing.

I have read a few articles stating this or similar types of opinions and even one up to 80%.

I think alot depends on how bad the nitrates are.



Scott

When I've moved my tanks over & condensed them into the big reef, it amounted to at least 150g of new water or over 50% water change. The corals LOVED it. I've done 35-50% water changes in the past with no problems, as long as the temp & salinity was the same.

....and now the post shows up....

The board ate my post....

For those of you who do larger water changes, how do you do so without exposing any corals placed high in the tank? Or do you just do as big of water change as your system can handle without exposing any corals, clams, etc.?

I do the water changes through my refugium and shut it off with valves from my main tank while I do the water change but I am not set up for any more water than I already do at one time.

Hopefully your skimmer will take care of your nitrates, along with water changes I'm sure your tank will be back looking beautiful in now time.

I also just noticed that you said you were using Reefresh on your system. How did or didn't the product impact your system while you were skimmerless?

I have drained all the water out of my 175g tank (right down to the sand) to catch the fish. The corals were out of the water for approx. 3/4 hour with no ill effects.
I have also had my clam out of the water when doing a water change. Do you know they can spit water over 6 ft and very accurately got me square in the face :lol:

I also unfortunately know this first hand. :lol: Sadly mine got me while they were STILL in the water and I was draining my 230g.

The ocean never worrys about corals being out of the water during a water change :razz:
http://forum.marinedepot.com/Attachment487.aspx

Lol!