Ben Brantley wrote:

SpectraPure's 5-stage RO/DI units include an optional
chloramine-removal stage... this, of course, is what I have. Do I
still need Amquel?

You would have to contact SpectraPure to ask that one.

What if I'm just concerned about excess phosphates and extremely hard
water? I have both of those here and neither seem like they'd be very
helpful in creating a healthy environment for discus and other
soft-water fish.

That, in a nutshell, is the justification for using RO water. Just brew your RO water, add RO Right as per the
label instructions to restore a bit of hardness, and your Discus will be as happy as they can be.
Not to go in circles, but the problem arises when you want to raise plants in the same tank, since most plants
want a bare minimum of GH 2. If you choose to add CO2 for the plants, the pH of the unbuffered RO water will
plumet toward that of battery acid fairly quickly.

Here is my formula:

72 gallon tank (actual water volume estimate 60 gallons)
CO2 bubbled in at 2 bubbles/second
100% Flourish substrate

Water changes:
20 gallons per week pure RO
2 teaspoons RO Right
1 teaspoon baking soda (Sodium Bicarbonate)
2ml Prime water conditioner

Result: GH2, KH2, pH 6.4.
KH will drop to 1.5 in about 2 weeks if I skip a water change.


Plant nutrients: I am three months into a fairly rigorous experiment with nutrients to control algae, so some
of these numbers are in flux.

Seachem Flourish 10 ml per week
Seachem Iron 3 ml per week
Seachem Potassium 18 ml per week
Potassium Nitrate 1/2 teaspoon per week

I also have 70+ biological ammonia production units in the tank, all of which are fat and happy.

The result is a tank overflowing with green and red plants, and most forms of algae gone. Green spot algae
still grows slowly on the glass, but I think that will be there no matter what I do.