alright for all you guys out there that are throwing TONS of clay into a tank to increase iron...let me tell you that you are sort of wasting your money and ill explain why.
first off, dirt already has plenty of iron in it in the form of Fe(3+)...even with PLENTY of iron in the soil...it can still be considered depleted if there is no good bacteria and decaying matter like leaves, grass cuttings, or dead branches in it. why this is is that good bacteria in the soil eat this decaying matter and turn Fe3+ into Fe2+ in almost anaerobic(without oxygen) conditions. here is the formula
H2O + Fe2O3(this is Fe3+) → 2Fe(OH)2(this is Fe2+) + O2
this Fe2+ is the ONLY iron that is usable in plants because they can absorb it while Fe3+ cannot be taken in by plants.
what does this mean to the aquarist?
put clay on the bottom of the tank before the dirt and gravel. this is usually where the least amount of oxygen is reaching...promoting anaerobic conditions.
mix in organic material such as peat, dead leaves, or fine mulch in with your clay to provide food for the bacteria.
mix peat in with your dirt also because dirt has TONS of iron in it that is just waiting to be released by bacteria.
what else does clay do?
as you all might know clay is negatively charged which means it likes to attract positive ions in the water. ions that could possibly feed nasties such as algae and unsightly bacteria. clay mixed in with dirt will draw these nutrients into the gravel/dirt where plants can use them via roots and where algae cant reach!
another thing that clay does is that it has MASSIVE amounts of surface area in its tiny cracks and pores(fired clay). these tiny pores provide a home for good bacteria that breaks down organic material in your tank and provides food for your plants. and another thing...the breakdown of organic junk produces CO2.
i hope this helps you guys understand what clay does and could possibly do in your tanks! enjoy
ADDED ON 1 DEC, 2011
so i was doing some reading and found out that rust is actually in the chemical form Fe2O3....the FE(3) form of iron!! so instead of adding expensive ferts to your substrate, iron enriched clay/gravel, nutrient enriched dirt, or w/e is on the market today.....this is my cheaper solution
organic potting soil - which already has all the decomposing organic nutrients and minerals that plants need
peat moss - provides extra organic material for bacteria to eat over A LONG period of time
iron - this can be obtained through such things as staples, nails, paper clips, or even old bolts and nuts that have been sitting in the shed.
the bacteria in your tanks will convert this rust into usable reduced iron that plants can take up. of course it'll be a very slow process for the iron to rust and be converted to soluble iron so add it early!
this was very interesting to read. So if I put leaves and other left overs from clipping on the bottom with the clay then it'll work better? Also isn't peat know for being sterile? So wouldn't it kill the bacteria around the clay? Adding these organic compounds to the dirt mix turns Fe3 into Fe2, that is very interesting. I want to try this on my next tank I set up.
what the peat will do is slowly decompose because it will turn the water acidic which will slow down the decomposing process. this will allow for the nutrients/iron to SLOWLY be released into a usable state instead of releasing it all in a short period of time. ive read about peat and its ability to both feed and hinder bacterial process.
it feeds by giving organic mater to bacteria and hinder by being pretty acidic.
i just set up my 120gal today...1 part peat, 2-3 parts dirt, and 1.5 inch gravel cap. ill upload a week by week up the setup from start to finish.
interesting. I have some peat soil laying around but it has a wetting agent in it so its no good to use I think. Does fired/ baked clay still give off iron or the other benefits since its cooked hard?
im sure fired clay gives off the same nutrients per surface area as soft clay...and being hard it allows for roots to have something to cling on to
so breaking up a clay pot or a brick into pieces and using it at the bottom of your tank would still be as effective?
This seems to make sense, I would like to seem some case studies and written evidence. Dont get me wrong I understand what you are saying, it would be cool to do one tank NO clay and another with clay. Lets see what happens, if anyone is interested in doing this let us know.
i just redirted yesterday with just peat and dirt...no clay. i have jungle val, sag, italian val, a melon sword, will be getting an amazon sword, and a few java plants.
Has any one ever used clay from the river in their aquarium? I want to know if there is any noticeable difference from that type of clay vs red clay.
i know dr. tim uses wild clay from the wild and he says its way better but i'm not sure if its the same stuff