usable Iron?

[SkullJug]

Hi all,

As some of you would know I have moved house and was supposed to have moved my tank about a month ago - I haven't had time yet (Have a three month old, makes it tricky!) which has turned out to be a really good thing, I have done a lot of redesign for my tank and have learnt HEAPS from this site. IT's the best community on the web IMHO.

My tank has always been really beautiful and gets a lot of attention from people who see it, but I think I can take it too the next level with a lot of the things I've learnt here and have a few questions.

The first one is about iron. I know that Iron has various forms, some useful and some not useful. In my previous setup I dosed Iron (WAY higher than I needed to) and waited until I had zero iron reading before re dosing, I did the same with Phosphate, I believed letting it run down like this would beat algae, funnily enough it always did but I now know there is a better way!! Does the fact that iron was being used up mean that it was in a usable form, or once it is not usable by plants is it no longer detectable??

I run a VERY slow RUGF and I dose all my ferts into this, so they only entire the water column via the substrate(and are taken up within the vermiculite within the substrate). The flow through the UGF comes from my cannister directly into an uptake pipe (Which is higher than the water level). I am assuming that at least some parts of my substrate is anaeorobic which I believes keeps iron in it's usable form but I am not entirely sure.

Can anyone tell me how the whole iron thing works? What is Chelate?? How do I ensure that the iron is usable? Why does an Anaerobic substrate keep iron available? Why can't Iron be mixed with macros?

My next question is easier and a real long shot - Does anyone know where you can buy dry ferts in Australia? - I have tried garden shops, bunnings, Hydroponics shops - to no avail.

Thanks all, I really appreciate the help!

 

[czcz]

Can anyone tell me how the whole iron thing works?

I'm no chemist or anything but maybe can give some input as a fellow hobbyist until the more knowledgable members post.

In part, Fe is important because we use it as a proxy to guesstimate the levels of the other stuff in comprehensive trace mixes (Flourish, CSM+B, Tropica, and so on). Tom Barr for one has argued that what we observe from high Fe isn't simply because of Fe, but because of more traces in general. I suggest using it to figure out what to dose and many concepts in this hobby.

While we do care about Fe specifically, just keep this in mind as you read.

The problem with Fe is that it falls out of solution when exposed to light, and falls out faster as KH rises. Once it oxidizes to the ferric (Fe +3) state, it is useless to our plants.

Does the fact that iron was being used up mean that it was in a usable form, or once it is not usable by plants is it no longer detectable?

I believe this depends on what the test kit is measuring. If it measures available iron (Fe +2), the drop in Fe could be because it oxidized to an untestable (and unusable) form (Fe +3) or was taken up by plants.

That said, I've been told hobbyist Fe tests are inaccurate, and so should be avoided.

What is Chelate?

A chelator binds to a metal (Fe), and a good chelator will keep it in the available state longer than a poor chelator.

The chelating agents of the mixes discussed here are all very good, but some are better than others. For example, many hobbyists using Tropica Master Grow (a product with an excellent chelator) dose much less Iron than hobbyists using other trace mixes. Some people go as far as to buy bulk Iron with the best chelators.

How do I ensure that the iron is usable?

Easiest way is to regularly dose usable Iron. Most dose traces every other day. Some go as far as to dose it every day.

You can usually see trace deficiency in new growth of plants, and it is highly recommended you keep a good indicator plant, preferably a fast grower, to guide your dosing. A good, easy, and common plant is H. difformis (Wisteria), which will turn yellow and pale with low traces, then recovers quickly once the deficiency is addressed.

Why does an Anaerobic substrate keep iron available?

Here's a great post from the APD. In short, Iron can't oxidize (Fe +2 -> Fe +3) if there's no oxygen.

(There's many other Fe related threads from around the net linked here.)

Why can't Iron be mixed with macros?

Iron can't be mixed with phosphate because they form an insoluable percipitate. This can be minimized by mixing them in a very large volume of water, such as an aquarium, and some report dosing them together with no issues. Best practice is to avoid the potential of percipitate by simply dosing them separately.

Iron can be mixed with the other macros if wanted.

Good luck!

 

[7Enigma]

Thanks czcz, I learned a great deal from this post (and that's getting tough around here since I've read almost everything! . Glad to know I can dose my macros with my liquid CSM+B, I had been doing it ever other day and it was somewhat of a nuisance. (I don't dose phosphate since its in my tap water and my fish/food/etc seem to always have the number slightly higher than I want anyway).

justin