"Toni" wrote in message
link.net...

"Rod Runnheim" wrote in message
...
In a healthy planted tank, the changes aren't to deal with Nitrate
levels,
but to add trace elements that would otherwise be lacking and are not
typically added as a fertilizer. There is probably a way to find all of
the
trace elements you would ever need and dose them carefully (based on
current
levels) and obviate the need for water changes. This would be terribly
complex however!



So... on average- how much how often?


I typically change between 15% and 20% every two weeks. I tried to get
away with less than that for a while, but the plants started to suffer.
A lot of this depends on your plants growth rate -- Very fast or very slow
and you may need to change more often or in larger amounts.

Rod