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RE: Pushak and Iron
Recently, Steve wrote the following in response to a question containing a
reference to Flourite:
> This is another example of confusion over the symptoms of iron
> deficiency. The red coloration of plant leaves is unrelated to iron
> availability according to reliable information by Diana Walstad in TAG.
> Red pigmentation is a protective response of plants to intense light
> which provides protection from UV radiation. It can be stimulated by
> intense lighting and possibly by the use of strong actinic lighting. In
> fact, I'm pretty certain that Justin's plants take on a red color of the
> leaves as the stem plants grow closer to the surface and get stronger
O.K Steve - I've got a question for you - I have two twenty gallon tanks set
up side by side, illuminated by a dual light fluorescent shop fixture
containing 2 F40C50 tubes (brand new Chroma 50's - 2 Watts per gallon). Each
tank was planted heavily initially with cuttings from the plants in my large
show tank. Filtration, CO2 input, water changes and fish load is either
identical or very, very similar in both tanks. Plant growth in both tanks
has been good over the past month, so much so that in one of the tanks it
looks like I may have to do some trimming soon. I haven't had any problem
with initial algae in either tank.
In one tank the new leaves on all the plants are a nice rich green, with the
Hygro polysperma leaves showing a prominent lighter green midrib (but note
that I would NOT call it chlorotic) and new growth on Ludwigia mullertii
coming in green. In the other tank, the new growth on Hygro polysperma
leaves is decidely pinkish and the new leaves on Ludwigia mullertii show a
strong red cast. Also in this tank, Ricca is growing in both a floating
clump and caught in among the base leaves of the stem plants (quite by
accident, but it looks great).
One of these tanks uses YOUR soil/PMDD method (which calls for Micronized
Iron in the substrate) and the other one uses a substrate composed of 100%
Flourite and gets Flourish and Flourish Iron supplementation.
My question is - which tank is which? You state above (or I should say that
Diana Walstad states, for you are only paraphrasing her) that red coloration
of leaves is unrelated to iron availability, it has more to do with the
intensity of the light. Lighting in both tanks is identical, and there is
only one small clump of floating Ricca in the tank with the pink/red leaves,
not enough to block out any signifigant amount of light.
Water chemistry parameters in both tanks are monitored on a weekly basis and
are well within acceptable ranges for newly setup tanks. Using a LaMotte
Iron Test Kit, both tanks fail to register Iron concentrations that are on
scale (0.05 ppm is the lower limit of the kit) but when viewed side by side
it is obvious that the test tube containg tested water from one tank is a
lot pinker (the expected color point for the test) than the test tube
containing tested water from the other tank. I would say that one tank
measures < 0.05 ppm and the other measures << 0.05 ppm.
Now, I feel that test kits are only guidelines and the true indicator of
tank health is visual, but I wonder what has caused the color difference in
the leaves in these two tanks. It isn't light, and Diana says that it isn't
Iron. You advocate Micronized Iron and one of these tanks has exactly the
amount you recommend, in the place you recommend (substrate). That tank also
gets 4 ml of PMDD weekly (from the formulation on your Website - which
doesn't contain any micronutrient component). The other tank gets every
other day additions of Flourish Iron (1.0 ml every two days) and a weekly
addition of 0.25 ml of Flourish and 0.5 ml of Prime. Weekly, 25% of the
water in each tank is replaced with water from a TFC Reverse Osmosis filter.
There are surely many ways to skin a cat, and many ways to grow aquarium
plants. Both tanks, as I have said, look good. One does look a bit nicer but
that may be more due to aquascaping than the health/growth of the plants. It
is way to early to say if one is doing a better job of growing nice plants.
But why the color difference, and in which tank is this color difference