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Re: Aquatic Plants Digest V2 #116
>From: Cynthia Powers <cyn at metronet_com>
>Date: Fri, 2 Aug 1996 18:39:06 -0500 (CDT)
>Subject: 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.
Niether GH testing nor a conductivity meter "account for all the
solids...". Plants need about 3 degress of KH and 3 degress of GH. You can
induce fish to spawn by adding RO or DI water at a temperature lower than
they are used to (think of a rainstorm), but the lowered hardness need only
be provided until the eggs are fertilized.
>
>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.
You need to reconstitute RO water, ie: add trace minerals. Bicarb alone is
insuffieient. Iron is the most important metal for plants. I use bicarb to
bring up KH only if GH is sufficient, otherwise I use a commercial recon
product.
I suggest a KH of at least 3.
>
>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.
>
RO units will produce water with varying degrees of hardness, depending on
water line pressure, water content and other factors. Think of RO as a very
fine mesh filter. DI water (such as produced with the Aquarium Pharm. Inc.
TWP) can be reconstituted "by recipe" because it is pure water, but I do
not believe that RO water can be. (ie: you have to test RO).
I used to have angels that spawned every time I did a 20% water change with
pure DI water at room temp.
Plants can take the reduced hardness for a short period of time. In a
general sense, plants need hardness mainly in order to grow. (same for
fish). You are right, however, in noting that a reduced KH will eventually
cause a plant "crash", especially in the presence of high nitrates. It
happened to me big time.
>
>Dionigi
>
-Bill Brady