Backyard Aquaponics
A place to discuss aquaponics

Trying to figure out my nutrient deficiency problems. I think it's magnesium however I do have a tomato plant which I understand consumes a fair amount of magnesium which is doing much better than the rest of my plants. Although I do have them planted in my first bed so I wonder if it's sucking up all the magnesium before it gets for the rest of the plants.i

There are a number of symptoms visible that suggest there may be a Calcium deficiency there, but it's difficult to tell from the one pic. From what can be seen I would also suggest there is probably more than one deficiency. Can you get a couple of pics of the new growth in the centre of the Bok Choy plant?... Not too close up, just from a better angle where the new growth can be seen clearly.

Can you show us some photo's of other plants in the system, the tomato etc?... and maybe some photo's of the overall system so we know what we're dealing with.

- How old is the system?
- What is the water temp & pH?
- What is the system comprised of, ie: FT, GB's, operating method (ie: F&D or CF), amount of fish etc?
- What are you feeding the fish?

Tomatoes are extremely efficient at extracting nutrient from the system, far more than most other plants. So much so that I actually recommend my customers don't put tomato plants in small or basic backyard type systems, rather grow them in a wicking bed next to the system and use the AP water to water them.

P.S. I just realised that the plants are in a DWC bed by the looks of it...

- Are you using mechanical filtration to remove suspended solids prior to the water entering the DWC bed?
- Is there good aeration happening in the water in the DWC bed?
- Are the roots nice and healthy?... a pic of the roots would be good.

The temp has been high sixties and ph 6.8. The setup is FT >radial flow filter>media bed>dwc. I honestly don't know what food I am feeding them. I bought the trout from a state licensed hat her at a tech school and he just gave me what they use. The system is 4 months old from beginning of cycling.

I should also mention that the radial flow filter really is not working efficiently right now. It needs to be retweeked but I was told since I have only a few hundred gallons that it didn't make a huge difference .

Looking at the new pics I believe there may be a number of deficiencies occurring, possibly Magnesium as you've suggested, but also possibly Calcium, Nitrogen, and maybe even Boron or Manganese.

In that situation it's not only difficult to diagnose a particular deficiency with 100% surety, but it's also difficult to provide a targeted approach to fixing the problem... a shotgun approach is probably the best course of action here IMO.

In saying that, there are a few issues that may be the cause of your problems and they need to be addressed first. Sorting them out could possibly rectify some, if not all of your nutrient deficiency issues.

(a). The water in a DWC system should be very clear. You'll always get fines settling in the base of your DWC bed, as it’s basically a settlement tank, but the water itself should be very clear. It should also be very well aerated. The roots of the plants should be very clean and white, or a slightly off-white. If they are brown then the aeration isn’t up to scratch. If you can see a build up on the roots, then your mechanical filtration isn't doing it's job, as you've suggested, and the build up on the roots is inhibiting nutrient and oxygen exchange across the root membrane.

Radial flow filters can handle a little higher flow rate than a standard radial flow filter, but many people overestimate their actual capability and have a flow rate that is way too fast. DWC beds don’t need a high flow rate through them, as long as the water in them is well aerated.

(b). RFF's and SWF's placed prior to any GB's are removing the overwhelming majority of mineral nutrients from your system.

(c). Ideally you wouldn’t plant fruiting plants into a new system, especially tomatoes. The system needs a few months to build up a nutrient bank, but that won’t happen if you have tomatoes in the system, as they are extremely efficient at extracting nutrient from the water.

My plan of attack would be to:

(1). Get the RFF sorted out. Even if you have to slow the flow rate through it and by-pass the extra flow back to your ST.
(2). Collect all solids from RFF on regular basis and run them through a mineralisation tank, add the nutrient rich water back into the system.
(3). Ensure there is adequate aeration in the DWC bed water.
(4). Remove any fruiting plants.
(5). Give any remaining plants a foliar feed with a good quality, full spectrum product, ie: ½ strength hydroponic growth solution etc.
(6). Add some dolomite lime at 1x slightly heaped teaspoon per 500L.
(7). Add Maxicrop, preferably the “with added Iron” version. Initially at 50ml per 500L, but in probably 3 or 4 stages over a day. Then weekly doses of about 20ml per 500L.

Also, and this is just my personal opinion... If you aren’t running the system as CHOP 2 with a number of separate flow loops, then I would have the water flow as follows:

ST > GB > RFF > DWC > FT > SLO > ST

...and put some red wrigglers into your GB's.

Woah! Thanks for taking the time to give me that feed back. I think that very well be the most specific and helpful information I've gotten to date on this forum!

Hi,
In the past i used a lot of the information on this forum to start my aquaponics and now I'm a member.
Thx for all the info,
but......
I’m also struggling to identify the problem with my bell pepper plant.
As far as I could figure out it seems like Magnesium deficiency but I’m not sure.
The older leaves is turning yellow and is falling off at quite a fast rate while the new growth looks healthy.
Any help would be appreciated, thx

Looks like magnesium - yellowing leaves with green stems are characteristic. Especially on older leaves (ones closer to the bottom)

I use epsom (bath) salts, and haven't had any problems with it as an additive.