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Re: Adding Iron
Caleb wonders why my advice differs from Tom's with regards to Iron
levels.....
I guess the short answer is "that's life......check the archives, when have
two people here ever agreed on how much of anything to add to your tank?"
In my reading of Tom's recommendations, both to you and to other members, he
seems to like to give his plants lots of everything - lots of light, lots of
CO2, lots of nutrients. While it obviously seems to work for him, I think
that there is a very real danger in going overboard if your tanks aren't set
up and maintained as his are. Very rarely here do people with questions tell
us _everything_ about their tanks and sometimes seemingly unimportant
details can lead to all sorts of complications.
Micronutrients are called that because plants need them in only tiny
amounts - the usually accepted dosing level of Iron, for example, is 0.1
mg/L. Now, actually _testing_ for that miniscule amount can be difficult
given hobbyist level test kits. I have a La Motte Iron Test Kit which reads
down to 0.05 mg/L and in all of the years of using it and maintaining around
0.1 mg/L of Iron (as tested by the kit), I have never noticed a deficiency
in my plants which could be pinned on a lack of Iron. In actual point of
fact, I rarely even bother testing any more - I rely on how my plants are
growing to tell me when to add or cut back on something. In _my_ tanks, if I
overshoot the Iron levels by adding more than I usually do, I can be
practically guaranteed a trip to "algae hell".
Most of the other micronutrients are required in even _smaller_ amounts than
Iron - for example, Iron is usually found to form approximately 100 mg/kg in
dry plant tissue, Manganese is found in levels around 50 mg/kg, Boron comes
in around 20 mg/kg, Zinc at 6 mg/kg, Chlorine at 100 mg/kg, Copper at 6
mg/kg and Molybdenum and Nickel at 0.1 mg/kg each. None of these amounts is
very much - they are all at least an order of magnitude (X100) less than the
macronutrients are found.
You also have to consider that just because you can test for something, that
doesn't mean that it it is in a form that plants can use, or that it can't
react with something else, either now or in the future, to give you quite a
different result from what you expect.
Every tank is apparently different, and every hobbyist's approach to this is
apparently different. But plants don't need anything near 1 mg/L of Iron (as
tested) in the water, and my caution to you is due to the fact that since
you are using a micronutrient mix which contains things in addition to Iron,
you could very easily see your tank, over the long term, develop levels of
some other micronutrients which could be potentially toxic if you shoot for
1 mg/L of Iron using the micronutrient mix as your Iron source. Ergo my
suggestion that you dose Iron using something which contains ONLY Iron, if
you want to have high levels of Iron in the water and to avoid potentially
overdosing some other micronutrients.
Liebig's Law of the Minimum still holds in an aquarium. More of a good thing
is not necessarily going to make things any easier or better.
Plants can absorb levels of nutrients far in excess of what they actually
need - but that doesn't mean that they will necessarily grow any better with
those excess nutrients inside of them - they simply store them. Learn to
look at your plants and see how they grow and react to changes in nutrient
levels over time (this is not a "dose this morning, react this afternoon"
sort of hobby - it takes weeks of observation and lots of patience).
Super high nutrient levels _can_ obviously work, when coupled with high
light and high CO2, but the margin of error at this end of the hobby becomes
very slender. And when someone takes only _some_ of the advice given and/or
decides to wait to adopt other parts of it, the carefully maintained balance
point can be thrown totally out of whack.
So, that's my experience.... and I've only been at this for around 30 years,
so I'm still pretty new.....
James Purchase
Toronto