RO water & plants

---------- Forwarded message ----------
Date: Fri, 02 Aug 1996 21:55:34 -0500 (EST)
From: DIONIGI MALADORNO <MALADORD%A1%RNISD0 at mr_nut.roche.com>
Subject: R.O. water and plants
To: AQUATIC PLANTS <Aquatic-Plants at ActWin_com>

Is there anyone around with experience on use of RO water and trace element
supplements in planted tanks? For my planted 180 gal discus (3 regular
greens and two Tefe greens) tank I am now considering the possibility to see
if reducing the water conductivity and general hardness levels I can induce
spawning. I am interested in evaluating the possibility to  try this in the
community tank, even if I fully realize that it would be much simpler to
have a separate breeding set-up. The reason is that I would like to observe
parental fish behavior in a less artificial environment than the standard
bare bottom tank. The prerequisite however is that there should be a
rationale for reducing water conductivity without severely depriving the
plants of the necessary nutrients.

I am not a chemist, and I will try to do my best in using correct concepts
and terminology: please do not scream too loud if I am completely off!

Currently I have in the tank 5 degrees GH and 2 degrees KH with a pH of 6.8:
from Degen's book "Discus in the community tank" I got a conversion factor
of 1 GH = ~30 microSiemens, but I am not convinced that this is correct,
since GH does not account for all the solids dissolved in water. I know for
example I have also phosphates (1.5 mg/l, slowly but constantly decreasing
thanks to improved plants uptake), nitrates (2 mg/l), humic acids and God
knows what else. Therefore, I do not know yet what the conductivity of my
aquarium water is, but I am estimating that it should be greater than 150
microS. From the reading done so far, my understanding is that a water
conductivity in the 80 microSiemens range should be a reasonable target I
could aim at for spawning wild discus.
Here are some thoughts on which I am interested in hearing comments that
might help me to understand the feasibility of this project:

1) I know my tapwater alone does not provide sufficient nutrients for the
plants, and I guess that PMDD supplementation of RO water (possibly buffered
a little with sodium bicarbonate to maintain 1-2 KH degrees) should still
provide adequate nutrients to them. If this is not the case, a nutrient
deficiency should occur gradually, and monitoring of the plant conditions
and return to the current water change procedures should prevent
irreversible crashes in the plant population.

2) does anyone know what is the conductivity of deionized water supplemented
with the recommended PMDD doses (1 ml/10 liters, if I remember well)? My
whole idea depends on whether or not I can use adequate PMDD amounts with RO
water, staying below ~80 microSiemens. As soon as I receive the tester and
the RO equipment I will of course be able to estimate that by myself.

3) The main think I should be concerned with in terms of serious
emergencies, is to loose control of the pH. If I maintain the current KH
levels, the occurrence of pH crashes should be less likely.

Thanks in advance to those that will give me comments. Please note that my
e-mail address is currently a little screwed: I was told however that
messages sent with the previous address (dionigi.maladorno at roche_com) should
still arrive to me.