Backyard Aquaponics
A place to discuss aquaponics

My system is new, running several months. About 1,000 L. total water, 25 talapia to 3". Things were growing great then I developed this browning problem. Is it lack of nutrients (too many plants, not enough fish) or something else.

The problem is on both my raft plants and those in the grow bed, lettuce and basil but not the cress.

Thanks

My immediate thought was that the plants were getting "splashed" by the nutrient water...

Although now I'm perhaps tending toward a fungal infection...

Have you done a test of your water lately? What were the results

my first impression was "root rot" and this may still be the case in a raft system where you don't have enough aeration under the raft..DAMHIK

Another question is, is the "browning off" crispy, if so then you could be looking something like a lack in potassium or even salt burn if you have over salted your system.. If it's just brown and limp then I would agree with Rupe and say that it's some kind of fungal infection possibly due to high humidity.

just a few thoughts,

Himzo.

Would have said possible "root rot" as well... but the "whiteness" of the roots poking out of the netting seems to negate that... although it's hard to distinguish what maybe inside the nettings, and it does concern me a little...

But if that was the case then I think the plant stems would be discoloured and perhaps thinning... ala collar rot...

Any heat wave/cold snaps in the last week or so?

I would also think its unlikely to be a nutrient deficiency. Could possibly be frost damage if you have had a cold snap but I would have thought the water right there would have moderated the temperature. On a second thought the foam insulation would stop the heat rising from the water and the leaf hanging over the edge is green and healthy. So that would be my first choice and a fungal infection second. Worth opening up the root ball too and make sure it is not rotting off inside I am not a big fan of net pots and would rather see the base of the plant bare once its big enough to support itself.

My tip is rust or tipburn.
This can be cause by many things...

Tipburn is mainly caused by calcium deficiency, but is associated with several other factors. These include hot weather, hot dry windy days, high nitrogen levels, water stress and problems that prevent lettuce taking up enough water (for example root rot). The right choice of variety will reduce the risk of tipburn.

Didn't notice the Hawaii when I suggested frost - probably not a big chance of that.
I haven't had any experience with calcium problems as all the waters I have used have been naturally high in that.
Isn't tip burn usually in the heart of the lettuce not on the outer leaves?
I still can't quite see it as being a nutrient problem - with nutrients the marginal or interveinal areas affected are usually really distinct and consistant across the crop but in this case different areas of different leaves are affected.

What is the humidity like? Is there much air circulation around the system?
What is the aeration like under the rafts?

And of course, what do the water tests and temperature readings say?

There are lots of things, especially heat that can make lettuce look shabby but I've never had basil do what yours is doing so I'm inclined to agree with Rupe that some sort of infection might be the case.

I've had this happen, though right at the end ofthe growing season when temperatures are cold.. I would'nt have thought this would have been an issue in Hawaii (maybe a local cold snap)...

I'm tending to agree more with rupe about a fungal thing, as it's also happening in the grow beds and only to the soft leafed crops...so probably a humidity issue.

Himzo.

I took some samples into the county ag office. They thought it might be fungal and kept some leaves for further testing.

It is definitely not due to cold. We did have a hot humid spell, but the problem was already there before that happened. It could be due to humidity and lack of air circulation, both of which are issues here.

It also may be calcium deficiency, which is also a general problem in this area. How would you up the calcium in an aquaponics system? The ag office said one challenge with aquaponics is the fact that you can't do soil tests, but this would also be true for hydroponics. How do they solve the testing issue?

My water tests fine. I have never added salt since the cinder in the beds comes from near the ocean and already has some salt content.

What's the pH of your system?

Knowing what your pH is will help in determining the best calcium supplement for the system. See most of us buffer our system pH with some sort of calcium carbonate which will keep pH higher. Limestone or shell grit work well for this and they provide calcium.

I believe Calcium Sulfate might be able to add calcium without raising pH but I've not heard much about people using it in Aquaponics since buffering the pH is usually also needed at some point.

One thing about calcium deficiency, it is only rarely caused by an actual lack of calcium in the soil (or whatever the plants are growing in.) It is more often caused by stress of some sort. With tomatoes, they often outgrow the plant's ability to move the calcium from the roots up to new forming fruit and this causes Blossom End Rot (BER) and this is sometimes caused by too much nitrogen. Intermittent drying out between watering can cause some plant's roots enough damage to stop them taking up calcium effectively. Other nutrients in excess can sometimes cause the plants to show deficiencies by messing with the pH or locking out nutrients.

If fungus is the problem, then more air circulation and more space between plants may be the key.

Hmmm.. so a possibilty then

Of course, I don't believe anybody discounted it C1.
Until we have more information, eg PH, NO2 and NO3 levels etc.. then add water temp, and how much salt has leached out of the cinder (i assume this is scoria) then throw in humidity and airflow for good measure...in other words "all things are possible, grasshopper"

H.