Backyard Aquaponics
A place to discuss aquaponics

Yeah I think he's using DTPA and not EDDHA that's what it looked like in his video clip.

I don't think postage will be that expensive and with the DTPA being 11% you'll only be using a little under half of the EDDHA so there's a saving there, the postage on my kilo of EDDHA from S.A. was around $12.00 so that's not too bad, I think this will be about the same I certainly couldn't go get it for that price.

I just ordered some from him too, I will be happy when I have something that doesn't send the fish tank red! and now I have a lot of iron leftover for the dirt garden i guess

I am curious how long the tank will stay red... I am guessing months

I think it will be red for quite a while, my system never lost any colour in a month even with 25% water change.

Make sure you keep your left over EDDHA in a dark container apparently it oxidizes when left exposed to the light.

My folks well water has a lot of iron before filtration. Could I take a little and put in the fish tank? It would probably be hard determining the dosage that way, so I assume there is a test kit available. Is this the same kind of iron that the supplements have?

Fleetwood:

I would test the water pH before you added it to your fish tank and yes there are a few Fe Iron test kits available.

I think API manufacture/sell an Iron test kit... they have kits for other things like Calcium, Phoshorus etc...

I have the Aquo One Iron test like Joblow, didn't see the API one when I was looking

I've been using DTPA because of it's stability range I normally get 13% Fe chelate.
I was wondering why somebody did refer to it as toxic! never get a proper answer!
this graph show which type of Fe to use for the given PH.
This is from my supplier.

How do you apply it Bioaquafarm, spray on foliage or add to water?

I would assume even sprayed onto foliage, it would mostly end up in the water.

After watching the video I was convinced that EDTA is not for me:-
https://www.youtube.com/watch?v=E4_hCAnymFw

It's EDTA that is toxic not the DTPA

This report gives a bit more info on EDTA toxicity:
http://www.epa.gov/opprd001/inerts/edta.pdf

It does not appear to be very toxic, other than causing trace mineral deficiency. The paper also gives a fish toxicity of 430 mg/L. To me, the toxicity at the levels used in AP does not appear that significant BUT the fact it is useless in high ph (7+) conditions means its a no brainer that its not much good in AP systems. It would also start binding Calcium at high ph potentially causing Ca lockout.

Does anyone in Perth want to buy some EDDHA?

I've some here in Melbourne and I think Tom up north has a bit also, so we've got the market cornered right across the country Mattyoga

Yeah between us we could colour every AP system red on both coasts

woops - I meant to say DTPA. You can keep ya blood baths!

I did a water change a few days ago, completely drained the sump & GB's Approx 500 ltrs replaced it with tap water 7.2 pH, then checked temp & pH between the sump and FT and then started pumping from the sump to the fish tank.

The colour did NOT change, it was still the same red as before the water change so that was a waste of time.

I have now added 25.5 grams of DTPA Chelated Iron to 1200 ltrs of water and the colour is starting to lose the red, so I think after 3 or 4 doses of DTPA it will return to somewahere near normal with a yellow tinge.


Whatever amount of Chelated Iron I put in I have never had a reading anywhere near 2mg/l, today the 25.5 grams still only reads as 0.25mg/l.

Here's my calculations:

2mg/l = 7.58mg/gal

DTPA 11% = 0.11

= 68.9090909 milligrams per gallon

my system 1200 ltrs = 317.006 gallons

68 x 317 = 21556 milligrams


21556mg = 21.556 grams


So at 21.5 grams I should be getting 2mg per litre, can someone please tell me if my calculations are correct and if they are why don't I get a reading of 2mg/l?

Joe