Chelated iron and zink

[John E Windsor]

I have found a liquid chelated iron and zink compound at Home Depot. I am hoping this will help improve the results in the system. Our tomatoes and peppers are small and sparse at best. There is some yellowing in the plants, but not real bad. Generally the growth is slow in all of our plants. Our seedlings start out good and then peter out. The pH is 6.4 to 6.6, NO2 is 0 ppm and the NO3 is at least 60 ppm. The ammonia hangs around .5 ppm. The catfish are happy and growing well. Our system is not quite 5 months old, but it seems it should be doing better than it is. Now, if I use this chelated product, I am not sure how much to put in the system. Thank you in advance for your help.

[Michael Welber]

Zinc in the water in my fish tank killed my fish after a few months. Be very careful about the amount. I only use iron and definitely not zinc. 

[Rob Torcellini]

The zinc is toxic to the fish.  If you have already added this, you probably should change out your water before you have any deaths.  I believe the iron/zinc mixture is used on lawns to help kill off moss.....

[John E Windsor]

Okay, no zink. Thanks!

[Phil Slaton]

John your posts are reasons that I went from Aquaponics to Aquaculture. 

You have veggie grow problems and fish challenges.  You fix one, and the other suffers or needs attention.  Except for my fry tanks, I only grow fish.  My wife can buy veggies at the farmer's market.  I ripped out 10 of the 14 IBC grow tanks and dumped the catfish in my pond.  I then installed 5 - 1300 gallon grow tanks - no veggies except with the fry tanks.  This is what the greenhouse or growhouse looks like now.

[Michael Welber]

It can be discouraging sometime. I go through the same emotions but have stuck with it. Of course, my "operation" is far smaller. My system alternates: problems with the fish and then problem with plants. 

[Leo White Bear]

John-

  Iron is good for the plants if they show signs of leaf yellowing, zink on the other hand will kill your fish in a short time.  One item you haven't stated was, where are you doing your system, geographically.  I am in central wisconsin and it gets cold here in the winter.  Unless I have a heated greenhouse to overwinter my system, I have to take it down and reassemble it the next spring.  Your bacteria takes time to mature to the extent to grow plants that you see in most of the pictures, lush, green and productive.  My small system is of a size I can bring into the house and I grow basil in it.  Over a six week period, from 1-inch transplants I have harvested an arm load of herb and it is ready to be cut again.

[John E Windsor]

@Leo We are in sunny central Florida.
Perhaps we need more than iron. Yellowing is the least of our problems. Our plants did well in the beginning, but now it is a real challenge to get things going.

[TCLynx]

Please describe the nature of the yellowing John.

See, if the new leaves are yellowing but the veins staying green longer, then it could be Iron that is lacking, However with the pH where you have it, Iron may well not be the problem.  If it is older leaves yellowing  then it could be some other deficiency.

Can you get some maxicrop (seaweed extract) into the system and see if the plants perk up?  What particular plants are suffering most?  Hot this time of year, many plants struggle.

[Tony Gilliam]

When you do put the chelated iron in, put in small amounts (in the grow bed). The iron won't hurt the fish unless they eat it before it dissolves. Buy putting it in the growbed you can be sure it will dissolve before entering the fish tank. I would add a table spoon and wait a day or so, then add more if needed. Depends on how the plants look. There is no definate amount needed, you just have to check out how the plants respond.

[John Cubit]

I guess my only question would be should I get a foliar spray or a soil application, and for that should I mix or use liquid?

[Michael Welber]

Murray Hallam advises putting one teaspoon into the bell siphons once a month. I've been doing that and it's been no problem at all for the fish. 

[Vlad Jovanovic]

Tony, I beg to differ, if I may, in that "...There is no definite amount needed..."...there is most definitely a threshold amount of Fe2+  that is needed in solution for plants to not show signs of deficiency. The exact amount differs for different plants at different stages of growth...but there is no reason to get that specific with it. Suffice to say, that keeping 2-3mg/ L (same as ppm) of iron in your system should be enough to stave off deficiencies in most any plants you might be growing.

The good news is that iron is very unique among the plant essential elements in that too much of it will not mess with a plants ability to uptake any another element. This is not the case with the rest of the base metal cations (potassium (K), calcium (Ca), magnesium (Mg) zinc (Zn) etc...too much of any one of those will set another(s) out of whack, they are antagonistic that way)...Anyhows...That being said, a good reason to shoot for 2-3 mg/ L is that quality iron chelates are expensive, so it might be worth doing the 5 seconds of math to figure out your threshold amount and to dose accordingly..

John, a decent Fe-EDDHA or Fe-DTPA chelate would be the way I'd go. EDTA has been proven to be toxic to plants quite some time ago, so I'd not use it on that basis alone. GrowMore sells a 6% Fe-EDDHA chelate product. The 10% product they sell is the EDTA variety...

If your plants are already showing deficiencies, it has been my experience that they react quicker to a foliar application than dosing the reservoir. If you are not looking to experiment and just want them to get better fast...foliar spray and dose your systems water to 2-3 mg/ L in the same stroke. I've never used the liquid chelates, I imagine they work the similarly to the powders.

I'm not sure what you mean by "should I get a foliar spray or a soil application"...