Re: Electric currents in tank

> From: George Booth <booth at hpmtlgb1_lvld.hp.com>
> > I wonder if there is any way we could make use of an electric field
> > in an aquarium like maybe to pull nutrients around with?  Maybe it
> > would make the plants grow better!
> As luck would have it, I have done just such an experiment.  

> Finally,
> the slow currents allow nitrifying bacteria in the substrate to reduce
> oxygen levels so that the trace elements don't oxidize.  
	Most of the trace elements are already in as high an oxidation
state as they are going to attain.  Zinc, copper and manganese will be
in the +2 state, and will not go higher under any circumstances we 
will see in an aquarium.  Iron will usually be chelated Fe(III), and
won't go higher either.  Boron and molybdenum will be there as oxo
anions (borates or molybdates), and _might_ be reduced to something
else in the substrate, but will not be oxidized further.

	The chelated iron will be Fe(EDTA)(H2O)-  Note the single 
_negative_ charge.  If the elements Zn, Cu, Mn are chelated, these
will be 2- ions.
> I am trying to force the migration of cations (positively
> charged ions like NH4+, Fe++, etc) down to the substrate and
> negatively charged ions like (NO3-) to the top of the tank.  The bare
> wire has a linear drop from 12v to 0v along its length; it is laid in
> a paired-serpentine pattern such that the two ends are together
> giving an average 6v field at that point and the average at all
> points along the length is 6v.  The DC supply is connected as a -12v
> supply, so the substrate will have a negative charge with respect to 
> ground.  
> I ordered
> some titanium wire from Edmund Scientific and ran a loop around the
> top of the tank just below the water surface.  This completely cured
> the fishes tendency to lean.
> - -------
> The results so far are nothing short of amazing. 
> About the only reason I
> can think of for this is the electric field: the Fe++ is being
> prevented from getting to the top of the plant or perhaps even being
> repelled by the negative charge at the top.  

	The chelated ions will migrate toward the _top_ of the tank,
but there may be some tendency to reduce the few positive ions around
to lower oxidation states, particularly if the oxygen concentration
in the substrate (near the cathode) is low.
> We do note a constant low level bubbling at the positive
> top wire and conjecture that the NO3- is being attracted to it and is
> being electrolyzed into N2 and O2.  This in itself is a significant
> advancement in the aquarium State-of-the-Art.

	One ion that is _not_ going to be discharged in this setup
is nitrate.  The major reaction at the anode will be:

	4OH-  ->  O2  +  2H20  +  4e

	The reason for using titanium is to prevent the reaction that
could take place with some metals:

	M   ->   M++   +   2e   (say) 

	The metal goes into solution, and you may get results you don't 
want from this!!!

	At the cathode, the I would expect the _main_ reaction to be
production of hydrogen.  Have you seen any bubbles coming from the

> As silly as this sounds, it appeared to be gold leaf.  
	Is this April 1st?     :)

Paul Sears   Ottawa, Canada