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Re: Fluorite and Iron

Dave Gomberg wrote:
> Steve, why not make up tubes of .02, .05, .1, .2,.5 ppm Fe and send them
> out to those of us who think we have this figured out.   Not necessarily
> one of each.   And ask us to report back our findings on the concentration
> in each tube you send us?   See whose test kit can tell and whose can't.

Well, I hope I'm not the only one with a scale! We have a selection of
test kits here in Vancouver; I think Olga has a good one so I'd like to
try it with hers. I have two different Red Sea test kits. I thought I
would limit the offer to folks in my immediate neighbourhood so as not
to have to mail chemicals into the USA.

James Purchase wrote:
> 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.
> But why the color difference, and in which tank is this color difference
> exhibited?

It sounds like you might be onto something James. Unfortunately I don't
have a theory. In my own tanks, the H polysperma which develops red
colour is the largest and most mature plants and only when they approach
the surface. Plants growing close to the surface receive more intense
light. Could it be that one tank has larger plants or that the growth
rates are also have an effect on the concentration of the anthocyanin
pigments? Are you harvesting any of the plants in either tank? Are all
of the plants in the "red" tank similar in appearance or could it be
related to slightly better positions in the tank?

You make a plausible case for overall plant health affecting
pigmentation however I'd hesitate to associate this to an abundance or
lack of iron.

I have to admit that I don't know which tank is which from your
description! It sounds fascinating tho...