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Re: Aquatic Plants Digest V4 #90
>> Frequently, people post about persistent problems with algae in their tanks,
>> and quite often their list of "tank parameters" include high color
>> temperature and often actinic lighting.
>I'd be interested to hear from anyone who had algae problems with
>high-Kelvin lights and solved the problem by making no change other than
>replacing the lights.
I found actually the opposite to be true with 7100K and 6700K PC bulbs. The
tank had 5400k bulbs prior. Adding the 7100 and 6700k things improved fast.
The 5000k range proved to be very good for algae with soured tank
conditions. Less than the 3500k seem to be tough on algae but good on
specific species of algae such as what I call haystack or hair algae that
tends to grow only on flourite and tubing etc but not on plants. Easy to
remove but actually a nice addition of algae.
Plants grew better without the 7100k added(just the 6700K's). **Perhaps
this** is what caused the "problem" rather than the spectrum and/or color of
the bulbs. Plants, that are happier, use more nutrients after all and
less(nutrients) are available for the algae. It seems that a *biological or
maintenance* issue rather than a light breaking the bonds issue is more at
hand in our tanks. A well growing lighting color, say 6700k, will cause more
iron to be used by the plants than a 7100k.
How much time is required and how fast can the plants get at it(Fe)? How
fast can the many different species of algae get to it?
Also many new plant people often get equipment that is not what many would
recommend for a plant tank. They(or you or us or I) perhaps might be blaming
the lighting rather than something else that may be causing the algae issue.
I would not recommend 7100k bulbs myself. 6700k definitely though. Many
folks get the 7100k and 6700k bulb mix. Later, they buy another 6700k or a
5400k etc to replace this 7100k bulb. So many folks try this set up. Little
changes except for the lighting. I still have the bulb(a 7100K) so if this
is true then there should be a higher iron level reading after I add it,
right? Free iron or/and chelated? A simple test should show some results
based on this adding and deleting a bulb. But............ how do you account
for the lesser plant growth(using less iron also now) based on the bad
growth associated with 7100bulbs rather than the bulb/lighting breaking the
bonds ? Seems like there would be a surge of iron if the plants suddenly
slowed down growth and the iron was not being consumed at the same rate as
before giving a false reading and assumption of light rather than plant's
growth rates as being the cause. Too many ?? and too little controls to draw
anything IMO. Test kits is a whole other ball of wax.
In another tank I used coralife 50/50 and a phillips ultralume and had great
results. I've tried many colors and types over the years and I came to the
conclusion that the lighting is important(intensity and photoperiod to a
certain extent) but the color is not as big an issue as some would have us
to believe. I run tanks from 3050K with quartz to 6700k PC and every thing
in between. I don't have this algae issue. Algae and spectrum or color temps
are not a factor IMO. Perhaps with Diana's set ups(soil and little water
changing) and systems but not with mine. If there are duplicatable results
across the board, I will buy this but I cannot say it for myself or my tanks
or other tanks I have done and seen. I need more proof for saying that 7100k
bulbs and higher temp bulbs make Fe available to algae. My tanks don't seem
to support it nor do many other tanks with high color temps. I think NA
bulbs by Amano's outfit run in the 8000k range. He seems to do well<g>.
>> In Chapter X of her book, on "Algae Control", Diana discusses Iron as the
>> limiting nutrient for algae. In oxygenated water, iron is generally found
>> bound, either as an iron precipitate (FeOOH, FeCO3, etc.) or is is bound to
>> dissolved organic carbon (DOC). Free iron (Fe++, Fe+++) are the only types
>> of iron that algae can use. So far, so good.... nothing really new here...
>> Diana goes on to explain that while rooted plants can get iron from the
>> substrate, algae depends upon free iron in the water column. Again, nothing
>I would have liked more discussion and documentation for the idea that
>algae can't use organically complexed iron. I felt even stronger about
>that when she also asserted that plants can't use organically complexed
>iron; other sources claim that plants can and often do use organically
I certainly buy Roger's notion. Plants can, do and will use it.
>Despite my reservations, I don't disagree with her conclusion. I find it
>very consistent with the common observation from people using PMDD that
>chelated iron over a given threshold (0.1 mg/l, I think it is) causes
>algae problems. The onset of algae growth at that threshold could imply
>that iron is growth-limiting at lower concentrations. However, iron is
>needed by algae in only small quantities and the threshold concentration
>is far too high for the chelated iron to be growth limiting. A possible
>explanation for the seeming contradiction is that the algae can't use the
>chelated iron -- they can only use free iron. The free iron might be
>there in a very low concentration that is generally proportional to the
>higher concentration of chelated iron.
>> But she explains that a common process called "photoreduction of iron" is
>> able to set the bound iron free:
>> DOC-Fe+++ + light -> Fe++ + oxidized DOC
>> Apparently, this reaction, which also takes place with manganese and copper,
>> can be greatly accellerated by light.
>I've read that this and other similar light-induced reactions with
>dissolved organics play important roles in some natural ecosystems. The
>original organics are typically stable and unreactive, but the
>photo-oxidized molecules are labile and can be used as food by bacteria,
>thus feeding an otherwise unproductive ecosystem.
The amount of light and the type (sunlight ) is quite a bit different than
The power and intensity is of sunlight can do all kinds of bond breaking
compared to our tank lights. At what level would this start to have enough
energy to break the iron free then?Again, more ????
>> Now this is "slightly new", at least to me... but the kicker is yet to
>> Diana cites research which indicated that UV and blue light induce the most
>> photoreduction because wavelengths of light below around 500 nm are
>> energetic enough to break the DOC-Fe+++ chemical bonds. She also explains
>> that iron can bind to a variety of chemicals and different types of DOC, and
>> that each separate "species" can vary in susceptibility to photoreduction.
This *could* likely be true.
>I haven't read her source for this, but from her description I thought
>that the control on the experiment might be inadequate for the conclusion
>she drew. There might be reasonable alternatives and other factors
>effecting the results.
>> Now, to me at least, this IS new information, and another reason to stay
>> away from 50/50 and actinic lights in freshwater plant tanks, especially
>> those with older substrates and corresponding high levels of DOC in the
>> water column.
With her set ups at least. I think the 7100k just don't do much for plants
**growing** generally rather than cause the iron to break into various forms
resulting in algae outbreaks.
My tank had only Fe added to the water column and that tank is still the
most algae free tank I've ever had.
How much light energy is required for this? Do our tank lights even have
this much energy(comparing it to sunlight)? What about the UV or very close
to this range? Sunlight has it but many(of course there's the tanning bed
lights!) tank lights don't have very much. A small amount of your
lighting(in my case 1 x 50/50 and 1 x 5000k bulb) can have 7100k or so
without any problems. They just don't grow the plants well. Bad plant growth
can lead to algae problems and less Fe being used up by the plants showing
more Fe in the water column perhaps making one think that there is more Fe
due to the light.
All or 50% didn't do well but a mix of 25% or so did do well. One of the
best algae free tanks I ever had was with a 50/50 bulb. Nothing in the
gravel at all(Fe)but lots of bacteria in the gravel, which lends a notion to
the DOC's and other species of Fe and the organic cycles in the substrate.
>I liked the emphasis that Ms. Walstad placed on dissolved organics in the
>aquarium. DOC can potentially play several important roles in aquariums,
>a couple of which she emphasized in her book. Unfortunately there's very
>little technical information on DOC in aquariums, no convenient tests for
>us to run and no body of knowledge that lets us understand the variability
>or controls on the types, amounts or effects of DOC in the aquarium. Its
>fairly easy (I know, because I've done it) to assert the importance of
>constituents that aren't quantified or well-understood. It's a lot more
>difficult to actually establish their importance.
Big time agreement here!
>> Many people (most of us I guess) use certain "aim points" for particular
>> nutrients in the water column - we want iron, to be at one level, phosphate
>> below another level, etc. Many of these "aim points" come from hydroponic
I think more needs to be done on the specific nutrients used for plants kept
These aim points are different for each plant too although some degree of
generalization can be done.
Diana reminds her readers that in tanks with enriched substrates
>> (her's are soil based), iron should really come from the substrate, not the
>> water - so our additions of chleated iron to the water column might be
>> counter productive and based upon research which is not really applicable or
>> appropriate for an aquarium.
>I wonder what proportion of the APD readers use chelated iron in their
>tanks. I'll guess that most of us do and that many of us use it without
>algae problems that can be attributed to the iron.
I do and I have no algae issue with iron. My iron levels are quite high in
fact is some tanks. But what is an iron level of .1mg/l anyway? Mine do well
at .2 or higher with no algae. I have some off the wall levels but yet the
plants do well and little or no algae.
Again, there are many ways to achieve a dandy plant tank .......not just
What works for her system might not for some else, but try everything and
see if you can do it their way.
>> Comments or thoughts, anyone???
>Ms. Walstad's point here is very interesting, but it's a point that I
>think may be more relevant to her soil-based approach than it is to some
>other successful methods. There are other places in her book where I
>found her ideas to be very interesting and well thought out, but difficult
>to factor into more general aquarium-keeping methods.
Agreed. I think it's a good well thought out book for her approach. Some of
the references are not supportive of her notions at times but most are(there
are *many* which is better than most books!). Thought provoking to say the
least! I think it's a great book and one that should be on the shelf for the
plant tank keeper. I'm glad to see it's not another "same old book". It does
accomplish the most important thing a book can do, make you think!