Backyard Aquaponics
A place to discuss aquaponics

Hi, I'm new to aquaponics and this forum. I've had my system a few weeks now -but it was an already cycling one from someone else so running okay. I found the veggies have been growing really well and the Nitrate is >40. However, I was getting yellow leaves. I dosed them with 2 tsp of chelated iron mixed in 10 l water and within 24 hours all of my lettuce were dead. I did water it in from above so maybe it shouldn't have got on their leaves? Or maybe I added too much (2tsp per IBC)? Any advice appreciated!

what is the pH of your system and what brand/type Chelated Iron did you use ?

Two tablespoons of Iron is a huge amount for an IBC system, especially if they were a heaped and not a level spoonful.

A couple of times now I have rectified Iron chlorosis in plants, in a matter of days, by adding what I thought was a 1/4 level teaspoon of EDDHA Iron into 500L of water, in a single IBC system. However, a couple of days ago I bought some proper measuring spoons and found out that what I'd been calling a 1/4 teaspoon was actually only 1/8 of a teaspoon... Moral of the story... It doesn't take much EDDHA Iron at all to solve Iron chlorosis issues.

If the amount you added was 2x heaped teaspoons into 500L of water (even 2x level tspns is a lot), then it very well could've led to an Iron toxicity issue... Contrary to popular belief, there is such a thing as too much when it comes to Iron. In saying that, I would be more inclined to point the finger at the weather, or possibly a combination of the two... It was 43ºC at my place on Sunday arvo, and 43ºC at the shop on Monday... Lettuce really don't like temps like that.

I have lettuce growing under lights in a display system in the front of the shop. On Saturday arvo they were fine, even the large lettuce directly under the light, but when I got in on Monday morning it's top leaves had burning around the margins (see pic below), obviously due to the high air temps on Sunday, because the plant had gotten any closer to the light.

One thing I will surmise from reading between the lines of what you've told us, is that you didn't use EDDHA Iron. That much EDDHA Iron would've turned your water very dark red. So I'm assuming you are probably using Yates chelated Iron, which is EDTA Iron... If your Iron chlorosis issue was caused by high water pH locking out the Iron, the EDTA isn't going to help, it's only effective if the pH is around 6.5 or lower... Even DTPA Iron, which a few people are recommending lately, isn't available to the plants if the pH is above about 7.0

You want EDDHA, which is available to the plants across a very wide pH range... In fact I've seen it stated in technical data as being available across the entire pH range... You just don't need to use very much... If your water turns dark red, you're adding too much, a pink tinge to the water is all that's required.

High temps Sunday & Monday: https://www.facebook.com/13720939299814 ... =3&theater

Hi, thanks for your responses, I used 2 flat teaspoons of 13% Fe soluble EDTA. My pH is 6.3 in one and 6.6 in the other. Thanks also for your advice about the EDDHA iron. I didn't know the difference. I did do a search on this site and found someone else who had something similar and it could have been nutrient burn. a combination of putting too much onto the leaves in hot weather...

Also, do I need a cover over my aquaponics? e.g. shade cloth or should the plants be ok in direct sunlight? (the fish are covered with plyboard lids)

check Charlies post here plus the other information for March 7th onwards.....
viewtopic.php?f=1&t=9599
[Thread = Chelated Iron Dose]


depends on your situation and what you are trying to grow,
being in Perth the summer heat can have an affect and it usually helps Jan-Mar (maybe Dec-Apr) to have some shade
(suggest 50% shadecloth rather than higher 69%/90% etc).
But once the heat drops off many plants will enjoy the full sun.

Some/many things don't mind a little bit of shade - so having a bit of afternoon shade is not too bad either.

also full sun can heat your media which in turn heats your water as water passes through the GB.
So your fish and FT temps can affect your decision to shade.

Great thanks Darren!