Iron & testing

Hi Everyone,

What follows is a conversation Kevin & I had earlier this week & I thought
others might be interested (I asked Kevin if it was OK to post it).


Date: Wed, 14 Jun 1995 11:07:12 -0400
From: Kevin Conlin <kcconlin at zola_cae.ca>
Status: R

On Tuesday, 13 June 1995, stevensj at calshp_cals.wisc.edu wrote:

> I was just reading over some old posts from the aquatic-plants list &
> I was wondering if you ever got your apparent iron-deficiency problem
> sorted out.

A couple of days after my last post, with carbon out and UV off,
I was finally able to get my iron level up to about 0.5mg/l.  As an
experiment, I turned the UV back on to see if the iron level would
quickly return to zero.  After four days the iron again dropped to
zero.  It's possible that the UV oxidizes the iron or the EDTA, but
the rate is low enough that I think I can leave it on if I fertilize
2-3 times a week.  I'll eventually post my results.

> I was also wondering what test kit you used.  It appeared
> to me that your test kit had it's lowest level at 0.25 ppm.

My test kit is made by Sera (the only kit I could find locally).
Three drops of reagent are added to 5ml of water and compared against
a color chart after a 3-minute wait.  The chart has color samples for
0.25, 0.5, 1.0, and 2.0 mg/l.  It's very hard to check the color with
the vial supplied with the kit because 5ml of water is only about 1cm
deep.  I switched to a tall, thin vial from another test kit and the
color is much easier to see.

> I use
> the Red Sea fish pHarm test kit which has readings in increments of
> 0.1 ppm.  I never seem to get past 0.1 (kinda hard to tell if it's 0.1
> or 0.2 ppm) no matter how many dupla or tetra tablets or drops I put in.
> I now just constantly have tetra hilena crypto tablets in the tank: they
> don't seem to dissolve if there is enough iron in the water, they stay
> pink.  At first the tablet dissolved immediately but now that I have
> 0.1-0.2 ppm iron the tablets don't totally dissolve for a few days.

Interesting!  I wonder if the tablets are made to behave that way to
prevent overfertilization by people without test kits.  Perhaps they
harden the water as they dissolve.

> I just use that as my measure of iron in the water - according to my
> test kit I'm far from ODing.

You've got about a 5-10:1 margin, so as long as your kit isn't totally
out to lunch you should be OK.

> The Tetra Hilena Crypto tablets are pretty cheap: $1.44 per box of
> 10 if you buy 6 or more boxes through Pet Warehouse.

For my tests I've been using ordinary iron chelate available at garden
supply stores.  $CDN 7.00 purchased a lifetime supply of the stuff.
Unfortunately, it's an iron supplement only.  Ed Tomlinson recently
gave me the address of a local hydroponics shop that carries Chelated
Micronutrient Mix, which contains everything except N and P.  $10
apparently buys a 6-year supply for 200 gallons of water.  Tetra
tablets are $6.50 a box locally, and mail order is a bit of a nuisance
because of duties and taxes, so I've never used them.
Kevin Conlin   kcconlin at cae_ca   "We're Canadians.  We HAVE to be polite"

Date: Wed, 14 Jun 1995 11:31:06 -0400
From: Kevin Conlin <kcconlin at zola_cae.ca>
Status: R

On Wednesday, 14 June 1995, stevensj at calshp_cals.wisc.edu wrote:

> would you mind if I post our "conversation" to the list?  I think several
> people may be interested.

Not at all.  Go right ahead!
Kevin Conlin   kcconlin at cae_ca   "We're Canadians.  We HAVE to be polite"