Re: Frequency of Fe fertilization

> From: "John Y. Ching" <jyching at watnow_uwaterloo.ca>
> Kent's iron fertilizer with Mg and K
> instructions say 1-3 tsp per 30 gal at weekly water change time
> I should use 3-9 tsp every 7 days. Instead I use daily dosages 
> of 1 tsp I was also concerned that
> use of a de-chlorine chemical at water change time would 
> neuralize the trace elements.

Hmm... Would that be 1-3 tsp for every 30 gals of water changed or 
for the whole volume of the tank? It would make sense to do it on the
amount of water changed since one might change 10% biweekly or 30%
weekly. The idea is to maintain a nearly constant concentration 
of the nutrients as opposed to building up the concentration.
You might be adding a bit too much?

WRT the de-chlorinator, as long as this is not a general purpose
water conditioner, it won't have anything designed to precipitate
heavy metals like copper, iron etc. Do you have high concentrations
of chlorine? Is there a noticeable smell of chlorine in your water?
You could contact your water department to find out how much
chlorine they are adding and if there are seasonal variations.
The Vancouver water where I live is very clean and they use 
little chlorine. I don't use a de-chlorinator with 25% water
changes but I use it whenever I've been using chlorine bleach
to disinfect plants, decorations or equipment of algae.

> I know that Dupla is a proponent of the daily Fe regime. How come other
> brands recommand weekly or bi-weekly Fe feeding with water change? 
> How long do the nutrients remain available to my plants in the aquarium 
> water anyway?

The use of daily supplements as opposed to weekly or biweekly is
ok. Fe and Mg both slowly precipitate out of solution as the 
chelating agent breaks down or gets eaten by bacteria. I think it
is also perfectly fine to use the weekly approach since the plants
are able to store Fe and Mg in concentrations many times higher 
than their immediate requirements. I think it would be a good
idea to try a Fe test kit if you are interested in knowing how
quickly it is used up or what your current levels are. The
Fe concentration would drop quite a bit over a two week period
however, even .1 ppm is much more than your plants actually need.

 Steve Pushak - spush at hcsd_hac.com - Vancouver, BC, Canada

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