Backyard Aquaponics
A place to discuss aquaponics

Hi everyone. I am having trouble with my plants in my new AP system. I am growing lettuce and asian greens (tatsoi, bok choy, komatsuna, mizuna). The lettuce is doing fine but the other plants grow well up until their first true leaves start to grow, then the cotyledon leaves start turning white and shriveling up. Then the plants just look sad and sick . I'm uploading some pics. Sorry they're so cropped, couldn't upload them straight from my phone otherwise.

My system cycled about 3 weeks ago. The pH has been 7.6. Ammonia .25-.50. Nitrites 0. Nitrates 20-40. I have added some maxicrop, didn't seem to help. I am using a high quality aquaponics fish feed.

I thought it could be something on my rocks, I'm using river rocks, but that wouldn't explain why the lettuce is fine The rocks passed the vinegar test and are very clean.

Thanks!

whats the climate like? is it really hot or cold? and what kind of lighting are the plants under? inside (artificial) outside (sunlight)?

How much light are they getting. if you are in NY I know you have to be inside. Are they getting 6 to 8'hours of sun or the equivalent?

Could be a mix of issues as well. It looks like possibly a fungal disease on the lower leaves that touched the media and I would trim these off. The upper leaves look like they have an iron deficiency and with your pH, I would look for chelated iron (there are different types, check out Nate Storey's video on YouTube). Sometimes disease or environmental conditions will make it look like deficiencies and that could also be involved (to cold for the type of plant or something along these lines).

Cheers

I am using T8 fluorescent lights, definitely not too close to them. It's always 55-70 degrees in the room they're in. The lights are on 16 hours a day. I thought I had an iron deficiency before, and the maxicrop I added has iron in it, the description said Chelated. If its a fungal thing, what can I do? Maybe I need to add more maxicrop. How much should I be adding? My system is one barrel cut in half, one half FT, one half GB, so probably has 25-30 gallons of water.

Not sure how much maxicrop to add.. i wouldnt think very much for that amount of water but I have never used it (could do more harm that good if you start adding it as you will end up with an ammonia spike a week or two down the track) maybe someone else on the forum can give you an idea of how much.

How much Maxicrop have you added so far? and have you been using it in a foliar spray as well? That can burn the leaves.

Also I don't believe that the iron in Maxicrop will be helpful in aquaponics as I don't think it will be soluble, especially at your pH. If it is iron that is missing then you might try to get some DTPA not EDTA.

I have never used lights myself, but is 16 hours a normal time to have them on? couldn't this be too much

I added a capful of maxicrop maybe last week. I added another capful today. Haven't sprayed with it. If it has chelated iron in it shouldn't that be good? What does DTPA and EDTA mean? Will I always have to add iron? Shouldn't I not have to add anything other than fish feed?

16 hours was recommended by a few sources for greens. The lettuce is doing great, and the Asian greens I've planted are brassicas which would like more light than the lettuces, so I really don't think light is an issue.

I will look into more iron info. I also read that adding worms to the GB might help, so I'm gonna order some worms tomorrow.

Thanks!

Here is a link to the video scotty435 mentioned
http://www.youtube.com/watch?v=E4_hCAnymFw
its good info on types of iron and he will do a way better job of explaining than I could...

Iron is one of the few things you will eventually have to add as it won't be available in the feed in a way that can be absorbed by the plants. Also you may have to add something to control the pH as later it will probably want to go down and down (eventually you will aim to have it between 6-7) so often hydrated lime (brickies lime) which you can get at any hardware store cheap will brink it down. Your pH will also depend a lot on the pH of your top up water which varies greatly from place to place.

I don't know how much if any of the iron in Maxicrop plus Iron is chelated based on the fact that I have never seen them advertise it as such, I could be wrong on this. Here is a page at Maxicrop describing the source of the iron and the type of iron found - http://www.maxicrop.com/pages/application_guidelines.html#liquidSeaweedIron

Basically it says -

Iron (Fe): 2.0%
Derived from ascophyllum nodosum seaweed and ferrous sulfate

Some of the iron may be chelated Some of the Iron is definitely not chelated and wouldn't help at the higher pH. How much of each is anyone's guess and what form of chelated iron is also anyone's guess.

The DTPA and EDTA is just shorthand for two different types of chelating agents that can bind iron. They release the iron within differing pH ranges and that's why Tom recommended the DTPA version. The video will explain some of this for you.

You will need to add iron at times and usually when you start a system is one of those times. I generally just add when I notice a deficiency develop but some do regular small additions. Here is a common example of how to use Chelated Iron.

Chelated Iron - 1 level teaspoon per 1000L every 6 to 8 weeks if pH is above 7.5 and iron deficiency is indicated.

If the pH falls below 7.5 the fish food should be supplying the iron and you won't need to add chelated iron. For most systems the pH will fall below this over time.

Many of the Chelated Iron products (like many fertilizers) contain very very tiny traces of lead and this is why I prefer not to add it unless I see a deficiency.

Cheers

Forgot to mention that you can spray on Maxicrop plus Iron as a foliar spray and this avoids the pH lockout to an extent. I don't recommend it in this case because it might exacerbate the fungal problem if that is what I'm seeing. I think it's better to get the proper Chelated Iron.

Great info, thanks so much guys! I'll check out that video and do some more research.


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