Backyard Aquaponics
A place to discuss aquaponics

So I see the comments to add MaxiCrop with Iron when your plants need it. Can't you just drop a few plain nails in the sump and let them rust? Or is this a different form of iron?

That rust would be in a form unavailable to the plants. And if the nail was galvanized, then you have zinc problems. MaxiCrop with Iron has Iron Sulfate in it, which is not a chelated iron. You want chelated iron. The three main types are EDTA, DTPA, and EDDHA.

Stay away from FeEDTA. It is not stable at the pH levels in most aquaponics systems, and the breakdown products aren't healthy. Most chelated iron products you see will be FeEDTA.

FeDTPA works at pH of up to 7.5, but it is highly photosensitive. In water with direct sunlight, FeDTPA has a half life of 30 minutes. If your tank and sump are fairly well covered, it should work. It causes a slight yellow tinge to the water.

FeEDDHA works at pH of up to 10, and is resistant to photodegredation. The downside is the "red fruit punch" look it gives to the water. In a black tank, you can forget seeing your fish unless they come to the surface.

No, I would never put in a galvanized nail! Defeats the purpose of getting rust

I did pick up some DTPA - nice to know I got the better stuff (though not the best). Nice to know what to expect in the water color change. Thanks.

Do you have an iron test kit?

No kit. I was just going to observe my plants for deficiencies. Didn't know there was a test kit.

Glad to see you got some chelated iron.

FYI: Maxicrop plus Iron can be used as a foliar spray if you don't have anything else. This avoids the pH issues of adding iron to the water in the system.

Iron Sulphate or EDDHA make good foiliar sprays,the red from the EDDHA is hardly noticeable when sprayed,as Scotty says about Maxicrop plus spraying will give you a quicker result to your plant,so is a way of helping things while you address the problem.,

The best info I've seen so far about Fe in AP is probably the Bright Agrotech videos:

Your linking methods did not seem to work (at least they did not how up on my screen)
Iron in Aquaponics
Iron in Aquaponics part 2-how much iron do you need

I found these videos (and most of the others from that youtube account) very helpful too.

I'm right on the verg of 7.5pH ..I think.. my API test kit does not actually have a color code for "7.3" "7.5" or "7.7" pH but my water comes up at 7.6 on the "low ph" and 7.4 on the "high ph" tests sooo I'm not sure if i should use the Fe DTPA, or Fe EDDHA: (really don't want to touch this one)

Check your pH at different times of the day and you may find that it reads lower or higher. If it's lower then you should be able to use the DTPA.

I wish everyone would do whatever you did to post the youtube links! I can see yours, but most posts with video links just have blank spaces.
I can go ferreting around the source to find them, but dont usually bother.

I just click the youtube button in the full editor and enter the video ID between the tags. No idea why it doesn't show up for some people. Works fine for me.

I found I can see the unseen through my phone's browser.. but not my desktops.. Could be my browser is out of date or my pop up blocker somehow thinks the coding for the videos on the forum is an add to be blocked, who know....