Iron Oxide in substrate

jameson_uk

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I have (not particularly regularly) added some Tropica root tabs under the sand. I have recently come across the Easy Life range which seem to be pretty good and are a fair amount cheaper.

They do some root tabs and when I asked what they were composed of I got
Root Sticks are made of baked red clay, without any added chemicals like chelators.
It contains mostly iron oxide (about 8,5%), some manganese, molybdenum, magnesium and potassium. No boron, copper, nitrogen or phosphorus.
If I have read https://www.ukaps.org/forum/threads/clay-balls.48828/#post-479609 correctly the iron oxide would only become available to plants if the substrate was anaerobic?

This is going back in time but I am sure that when I setup the tank I only used about 5cm of substrate (and probably more like 3cm at the front) to ensure I didn't get any anaerobic spots as I am sure the masses told me this was bad.

Would these be pretty much useless as a source of iron in my setup?
 

dw1305

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Hi all,
I have recently come across the Easy Life range which seem to be pretty good and are a fair amount cheaper.
They definitely aren't going to do any harm.
If I have read https://www.ukaps.org/forum/threads/clay-balls.48828/#post-479609 correctly the iron oxide would only become available to plants if the substrate was anaerobic?
Yes. In reducing environments ferric (Fe III) salts will be reduced to ferrous (Fe II) salts and these are much more likely to be plant available.

This maybe one reason why aquatic plants have leaky roots ("radial oxygen loss"), the oxygen in the rhizosphere will oxidise ferrous iron and reduce iron toxicity. Iron is like a lot of micro-nutrients, plants need some, but too much is toxic. There is a lot of work with Rice, mainly because it is the only really important crop that grows as an emergent aquatic.
Would these be pretty much useless as a source of iron in my setup?
My guess is that they won't have much available iron, it would depend a little bit on the temperature of the baking (calcining) process. The higher the temperature was the less iron would be potentially available, even if there were areas of low oxygen in your substrate.

If you think of a red brick, you know it contains iron because the iron oxides have made it red, but if you dunk it some water (even entirely de-oxygenated water) and leave it for all of eternity it will still be an intact brick at the end of it all.

cheers Darrel
 

tiger15

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If it is made of baked clay, then none of the elements listed are biologically available. Baked clay is used to make terracotta solders in China that lasted millennia with no degradation. It's ludicrous to list permanently bounded elements as nutrients as they are biologically unavailable. For example, you will never need oxygen for your fish as oxide is ubiquitous in rock, substrate and the glass box that contain them.
 

jameson_uk

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Hi all, They definitely aren't going to do any harm.
I didn't buy them as this is what I expected. I looked at them based on cost but also the Tropica capsules end up with the little resin balls which seem to find their way to the surface over time.

Guess I will just stick the with the Tropica ones which are complete ferts then. (I suspect they are basically osmocote but have never had the time to make my own)
 

dw1305

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Hi all,
Guess I will just stick the with the Tropica ones which are complete ferts then. (I suspect they are basically osmocote but have never had the time to make my own)
These are "controlled release fertilisers" prills, osmocote is probably the most likely source.
It's ludicrous to list permanently bounded elements as nutrients as they are biologically unavailable.
Yes it is down to the temperature of baking. It might be low temperature treatment (basically just to dry them out), in which case you would still have some CEC and nutrient availability, but (as you say) if they are fired at 500oC they are as much use as the "Terracota army".

We've had this discussion about <"laterite in the past">.

cheers Darrel
 

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