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Re: Iron levels


Glad to hear from you again, Neil!

On Fri, 27 Aug 1999, Neil Frank wrote:

> >Incidentally, dissolved iron in unpolluted natural water is generally in
> >the parts per billion range - 50 parts per billion or so is fairly
> >common.  The EPA limit for domestic use is 0.3 mg/l of iron, and their
> >limit for protection of aquatic life is 1.0 mg/l.  Why would we ever need
> >0.5 mg/l of iron in aquarium water?
>
> Simple... in nature, there is an unlimited supply. Generally, there is
> plenty of iron in the substrate... and even if there weren't, there is a
> constant supply at the naturally low concentrations. In a closed system
> without a refreshable supply, it must be added periodically. Otherwise it
> goes to zero. I suspect that you could do well with actively growing plants
> if you maintained a small but measureable amount (say .05ppm) as long as
> you keep it replenished -- perhaps by adding a new small amount many times
> per day (i.e. after measurements showed that the Fe was zero). I personally
> prefer the approach of adding the appropriate amount once per week. Towards
> the end of the week, the Fe concentration drops off... but that suits me
> fine. Otherwise I end up with too many or gigantic plants.<g>

Ah, sort of "binge-and-fast" plant feeding?

I know that works, but my preference is to put the iron in the substrate
and to judge the need for further additions on the basis of the plants'
growth.  This avoids all worries over appropriate dissolved iron levels,
which kits work and how, how often the water needs to be tested or how
often the iron needs to be dosed.  It's simple.  I like simple.

Were I to return to dosing in the water column I would probably see
increased growth in algae and in potential nuisance plants like Java moss
that are currently pretty well behaved.  But for the exercise I figured
out how much of my on-hand iron fertilizer (Tetra Florapride) I would need
to add to my 55 gallon tank per week to balance the approximate amount of
nitrogen I add to the tank with fish feedings.  I neglected the amount of
iron in the fish food.  It came out to less than 4 ml per week - enough
to bump the iron concentration up by 35 micrograms per liter.


Roger Miller