What % water change alters nitrification process?

[yuran22]

I have been battling high nitrate levels, and 10-20% water changes have not been effective. I'd like to do a 50% or higher water change to see if that does it.

Any thoughts on what % water change would result in the removal of too many nitrifying bacteria? Thanks!

[HighlandReefer]

If you were to do a 50% water change it is very close to the same as doing two 25% water changes (which would be 46.33% changed). That is you will remove very close to 50% of the nitrate and bacterial in your water. Bacteria reproduce very quickly, so it will not have a lot of effect on them. It is not recommended to do more than a 30% water change at one time, so I would do one 25% change and then change 25% the next day. The result will be pretty much the same as one large water change and much safer.

If you have been doing say 30% water changes per month and this has not reduced your nitrate (the nitrate is still rising) then you will need to do additional things to help reduce nitrate. If your nitrate has been staying steady with your current monthly water changes, then increasing the monthly total water changed will help reduce the nitrate. Water changes can be an expensive method for maintaing nitrate.

Randy provides more details in this article:

Nitrate in the Reef Aquarium
http://www.advancedaquarist.com/issues/august2003/chem.htm

[HighlandReefer]

Randy discusses the difference between one large water change and multiply smaller water changes adding up to very close to the same amount in this article. You will find from his charts they are very close to the same. ;)

Water Changes in Reef Aquaria
http://reefkeeping.com/issues/2005-10/rhf/index.php

[yuran22]

Thank you kindly for your reply. Very useful information.

[bertoni]

Most of the useful bacteria live on underwater surfaces, not in the water column, so the limiting factor for water changes is the tolerance of various animals, etc, to air exposure.