Backyard Aquaponics
A place to discuss aquaponics

Hi, my leaves were rich green for a while, but then slowly went yellow.

I purchased some Yates chelated iron, and had no idea how much to add. I guessed based on the recommended amount per square meter, couldn't really tell any difference in leaf colour, perhaps slightly improved.

After researching further, I found the recommended calculation:

2mg/L of iron per 3 weeks
Taking into account the % of iron in the product (12%), I need to add 5grams of chelated iron powder for my 300L tank.

One source advised that between 2 and 3mg/L of iron should be maintained.


Leaves still yellow, so I also purchased an Iron (fe) tester from my local aquarium store, which showed just about 0.25 mg/L. So I added some more.

A week or so later, I tested again to find 0 iron detected.

Added slightly more than the recommended amount, and tested again. Still 0.
Next day added double quantity - tester still not detecting iron!

My pH is 6.4, so it should be effective. Surely the plants are not using it up that quickly?

What iron testing kit are you using? And does sunlight touch your water?

Purchased Iron (fe) testing drops from local aquarium shop, I'll have to check the brand.

One tank may receive a small amount of sunlight, however my seperate tank is fully covered on all sides, and still showed zero levels after adding iron. At the time my pH was 6.4, so the Yates brand EDTA chelated iron should have been fine. At one time it showed a small reading of 0.25mg/L, but nothing since.

Apparently EDTA iron may not be effective at high pH levels (as is currently the case in my newer system) so I am looking at purchasing DTPA iron from a local supplier as recommended by mattyoga.

http://www.duralite.com.au/iron-dtpa-dissolvine/

Hi Asi, your post was a couple of mths ago but just in case your iron levels are registering but your plants are still yellow.....whether its because of iron def' I wouldn't know BUT....
I am reading a lot on iron chelates of late and there is a difference between the 3..
both ferric /ferrous and EDTA/DTPA/EDDHA.
The chelates from bunnings i can tell you is EDTA, not much good at all and a waste of money with ph's over 6.5. you may get a reading on your tests but the plants may not be able to uptake this.
THE DTPA is ok but useless with ph over 7.5.
The best is EDDHA. easily taken up by plants and suits ph from 5 right up to about 9..
there is a link somewhere on byap which takes you to the vertical gardener explaining these differences..

I have been using it from bunnings and have never been able to correct the yellowing on any of my plants no matter how much i add..
Ive ordered some of this EDDHA and it wouldn't surprise me if the yellowing all disappears..
.

Hi mudeye, yes I did the same thing using Yates EDTA at first. Later purchased DTPA from a Hydroponics wholesaler.
I think my (aquarium) iron tester isn't detecting the iron properly. Although after rebuilding my system, most kale leaves are still yellow. Ph up around 7.5 at the moment. Not much growth except the watercress...


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Be very careful using the EDDHA Chelated Iron it turns the water red and you wont see you fish for a while

Red will be a nice change from yellow......and providing the red will make it all green will be good.
cheers

We're talking really RED

The iron test may not be designed to detect the chelated iron. I guess what I'm trying to say is the test may be working as designed but just doesn't catch everything.

Bit hard to tell but the kale looks more like a nitrogen deficiency than iron to me.

As far as the iron is concerned if you spray apply the iron you'll avoid some of the pH issues that putting it in the system water causes. The bottle may have some instructions for this.

and if you apply to some leaves and not others you'll know straight away if iron was the issue, if the treated leaves respond.

Some test kits don't read all types of Chelated Iron the Aqua One Iron Test Kit will read EDDHA but not DTPA

viewtopic.php?f=1&t=24255&hilit=chelated+iron+test+kit

Figures! Can anyone recommend an iron tester that will detect DTPA?

I use one of these http://shop.hannainst.com/hi721-iron.html Seems to work well. I supplement with DTPA iron and there's very clear correlation between how much I add and the testing results. I can now easily keep the iron around about 2 ppm.

Note that the picture shows 15.0 ppm but, lower down on the page the specs say range is 0 - 5.0 ppm. So I think the picture is dodgy.

Not cheap although I think I got it for a little less on eBay.

Yep I got one too (721) - it measures DTPA well - takes about a week for levels to drop in my system so I have to dose weekly.