"if GH and KH are each at 2-3 or greater" Can you please elaborate on this
?
Do you mean the delta between GH and KH or their degree (which is soft....)
10x

gizmo
"Dave Millman" wrote in message
...
gizmo wrote:

Dave I couldn't agree more with you!
I also believe and from own experience there is no need to use RO water
for
planted tanks (unless you are breeding apistos.discus etc.)
I have a 100 gallon planted tank which I've once mixed 50% R.O water but
now
I use only tap water.
Our water is hard (GH 20d) but they do tend to get softened in the tank
after sometime (peat) I also have a CO2 system - do I get a PH value of
about 6.8.
Plants seem to be happy and growing well. The myth is what 'bothers' me
most. Is it better to mix like 50% or to use 100% tap water for the long
run
?
I know this question is a bit wired and mostly depends on tap water
parameters. Is there any disadvantage using 100% tap water ?

Here's an interchange I had with Chuck Gadd on this list about a year ago.

On Wed, 04 Sep 2002 13:55:26 -0700, Dave Millman wrote:

Of all possible aquarium plants, extremely few "require" low hardness
water. This is usually an old myth perpetuated by folks who don't grow
plants.

This was usually thought to be true because plants grow well with CO2
injection, which lowers the pH. And a low pH is usually found with a
low hardness. So, someone who doesn't grow plants decided that the
low pH (and not the CO2) was what led to good plants growth, and they
figured that you can just get a low pH with soft water.....


So the answer to your question is, no, there is no disadvantage to using
100%
tap water, if GH and KH are each at 2-3 or greater. For plants, the harder
the
better in virtually every case.