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Re:CO2 and light levels and alkaline desert soils and plant/fish ratios

Bruce (BErney1014 at aol_com) wrote in reply to my request for more info.
about what went wrong when he tried different balances of plants and fish
load, specifically what went wrong when he tried a lot of plants and a
small amount of fish:

>Once a thick jelly like slime covered all the roots of floating plants. The
>entire root mass, not a snail blob. The gravel started to turn black in spots.
>Overnight death of all the fish. Just one example.

This certainly doesn't sound like what would be expected with a high ratio
of plants to fish.  It sounds like a lot of easily decomposable organic
matter got into the water.  The jelly-like slime was bacteria, and the
black in the gravel was iron sulfide, caused by anaerobic (oxygen-free)
conditions right at the surface of the gravel.  No wonder the fish died.
This sounds like what can happen with a  DIY (yeast-produced) CO2 setup,
where some of the contents of the yeast culture are being forced into the
tank somehow.

>I kept trying hygros for their fast growth. They grow fine (except for profuse
>"air roots") but other plants wouldn't.

The production of above-ground roots is a feature of Hygrophila.   You
gotta live with it.  My guess is that you had H. polysperma, which grows so
rapidly and easily that it can quickly take over a tank and keep other
plants from getting very far.  H. polysperma has to be trimmed every week.
The other plants might seem to be not growing at all, compared to H.
polysperma, but be patient, and keep the Hygrophila under firm control.

>I couldn't get a balance that helped all the plants so I switched to bottled
>co2 thinking it would help. It had the reverse effect. The plants lost color.
>Fertilizer created algae instantly. (Flourish.) That really stumped me.
>I believed all along I had a water chem balance problem. High 8.3 pH due
>to >WC bumping it up to "keep the color out". (caustic soda)

I can't tell from the above whether the loss of color was due only to the
use of CO2 or to the use of caustic soda.  Loss of color could be iron
deficiency, in which case the symptoms would show up in the new growth.
Pushing up the pH can make iron less available.

>I added fertilizer and instant algae. Water change after change in a week
>perked the whole tank up. Anubias nana lost yellow and greening. (there's that
>water chem theory again) Added spray bar shooting down, stirring the
>thermocline. Growth at last and algae gone. Gravel is warmer too. I had
>noticed my gravel was actually chilly.
>I was so distraught I didn't bother to learn (remember) many proper names,
I recommend keeping the ratio of plants to fish high until the tank has a
thick growth.  If you want to bring your pH up add a little lime or ground
limestone, not caustic soda (NaOH).  Don't worry about your pH unless it is
going below 6.0. Moving the water improves the uptake of both nutrients and
CO2 by the plants and gives them an advantage over green water types of

Hang in there!

Date: Thu, 24 Dec 1998 14:20:50 +0100
From: "Ole Larsen" <bse9195 at vip_cybercity.dk>
Subject: Sv: Aquatic Plants Digest V3 #728

Date: Wed, 23 Dec 1998 20:34:09 -0600
From: krombhol+AEA-teclink.net (Paul Krombholz)
Subject: Re: Light and CO2

From: "Ole Larsen" +ADw-bse9195+AEA-vip.cybercity.dk

>...On several occasions on this list have  I seen the need/use for CO2
>connected to the amount of light. This might be true, but not necessarily
>the way we all think (more light, more CO2).
>At last years symposium at Aqua Plantae Scandinavica, biologist Ole
>Pedersen, Tropica, told of some research, which at least to me, was new.
>The ususal "rule of minimum", saying that any organism needs so
>many factors (nutrients, lights, temp., ect)
>fulfilled in order to grow, and if any of these is in shortage, the
>>growth will suffer. This rule does not always hold absolutely truth: Some
>plants, about dying from lack of light (energy) was given extra CO2 and
>>started growing well. It was a strict scientific research and please
>>don't come back on me asking about double-blinds, statistic significance
>>etc.,I'm not a scientist, but I know when to listen.......

  Quoting Paul Krombholz----

  >>I have found that increasing the CO2 for poorly-lit Cryptocoryne
  >>caused severe melting. However, if the lighting was increased from one
  >>twenty-watt fluorescent on a 29 gallon tank to three twenty watt
  >>lights, increasing the CO2 caused only a very minor melt of parts of
  >>the oldest leaves, and then the plants started growing vigorously.

>Sorry I do not remember the kind of plants involved, but it certainly was
>>not c.+ALQ-s. But kind of plant was not the issue. The issue IMO was that
>>the "rule of minimum" isn+ALQ-t always correct and when it is, it could
>>be that it is a matter of a gradual change.

If some plants were "dying from lack of light energy", but they started
growing well when given extra CO2, while, presumably at the same levels of
light, then, perhaps, the rule of the minimum still holds.  The rule of the
minimum, attributed to Liebig, a famous German agricultural chemist, states
that the plant's growth is limited by whatever factor is in the least
supply, and increasing the supply of other factors, in greater supply than
the minimum factor, won't help growth.

My interpretation of the results is that CO2 was in the least supply, not
light.  It may be, at higher light levels, the plant would be able to
extract CO2 more efficiently, but at THAT light level, CO2 was limiting.

I don't have an explanation why my crypts melted so severely with high CO2
and low light, but melted hardly at all and then started growing rapidly
with high CO2 and high light.  I am quite sure, however, that it was the
condition of high CO2 and low light that caused the melting.  The crypts
had been growing very slowly in that tank for several years with low CO2
and low light, and the only change I made was to start adding CO2.  The day
after I started adding the CO2, I saw a small amount of oxygen bubbles
given off, which I had never seen before---evidence of increased
photosynthesis.  About three days after the start of CO2 additions, the
meltdown started and continued for more than a week, at which time there
were hardly any leaves left.  I then stopped the CO2 additions, and, over
the next several months, the plants recovered.

Have a happy New Year!

>Date: Fri, 25 Dec 1998 01:02:26 -0700 (MST)
>From: Michael D Nielsen <mnielsen at U_Arizona.EDU>
>Subject: More light and lots of it

>.....Last thing.  I live in Tucson AZ and as Steve (?) has pointed out
>>using the alkaline soils found in many deserts is not the best of ideas
>>so using the go out and dig up a soil is not real feasible.  There is
>>some river soil which may be OK, but is very young and of generally poor

The alkalinity in desert soils is due to sodium bicarbonate and can be
easily leached out with rain water or distilled water.  Put the soil in a
plastic dish pan or shoe box, slope the soil from front to back, with the
soil starting from a few inches back of the front, and gently and slowly
flood with rain water until the soil is entirely covered.  Let it sit
overnight to give time for the bicarbonate to diffuse out.  Then siphon the
solution out while gradually propping up the back of the pan to drain the

Paul Krombholz, in cloudy Central Mississippi with rain on the way.