> So, if you add trace elements (via Dupla drops, or poor man's dupla drops),
> does this mean that you can cut back water changes in your rainbowfish
> planted tank to once every couple of months?
Only if you want ulcers. :-) Irrespective of natrate levels, rainbows don't
seem to do well in aquaria with high organic loads. It is probably not the
organic material per se, but general levels of negative bacteria in the
aquarium. (that's my guess anyway)