For the fish you want to keep: you don't need the RO, unless breeding
is a serious desire.

Use the tap, it's fine. Add CO2 and don't worry about PO4. You may
need to add PO4 in relatively small amounts, the PO4 they add to water
systems/or that may be present in well water etc is not enough to have
a significant effect on the pH/KH issue except perhaps in very extreme
cases.

Using pH buffers is complelety out for a simple reason, plants do not
grow on "buffer" and plants are not made up of 40+% dry weight
"buffer", they are made up of 40% + of Carbon.

So add what the plants need, CO2, the plants do not care about pH,
they do care about good CO2. A plant will grow just as well if not
better at a pH of 7.4 and a KH of 20 as it will at a pH 6.4 and a KH
of 2.

Both pH/KH's above have 24ppm of CO2.

It is a _myth_ that plants "prefer" soft water.
If you want the plants to grow better, add CO2.

You may want RO for the fish, but it's not anything anyone needs for
the plants.

I've been through this with dozens upon dozens of people over the
years and they now have plain tap water, Cardinals, Rummy noses all
doing great in their hard tap water, and my own tanks have had very
hard tap water in the past also and these same fish.

Some folks needed me to tell them you don't need RO 25x before they
got it, but a few years later they thank you.

I've done this myself and am not citing some myth ridden books of
years past. If you claim to know of a soft water only true submersed
growth plant, I'd like to hear about it. I've raised 250+ species and
ain't found one yet.

Regards,
Tom Barr




Regards,
Tom Barr