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I have a small indoor aquaponic system for about 6 months now.  I am having trouble getting green peppers and tomatoes to start.  The plants look great but no vegetables/fruit.  Basil looks good, some lettuce, but no green pepper or tomatoes.  What am I doing wrong?

System information:

2 grow beds - soon to be 3

180 gallon fish tank

32 tilapia fish of various sizes

PH 6.4-6.6

Ammonia:  <0.25ppm

Nitrate:  <0.25pp,

Nitrates:  0 ppm

Fan:  on for about 1 hour a day - also shake the plants every few days.

Add iron:  1/2 to 1 tsp every 2 weeks.

thanks for your help.

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Good pruning and "cutting back"" techniques can encourage tomato and pepper bloom and fruiting.  Also, peppers seem to need a cooler period of the day to process all the goodies they uptake during the rest of the hotter/warmer day.


Trimming out  those suckers and deformed/damaged leaves helps a lot. And one neat thing about indoors is a very long season.

I suspect your system is so new it is short on potassium and maybe a few other nutrients. I have had similar issues I the past and was able to top up with potassium chloride and Epsom salts here is a thread where Vlad stepped mee through some of the details.

Most people stick with non fruiting plants for the first year or so but I am not that patient LOL.
Good luck.

In one of the pictures, it looks like I can see a flower.  I wonder if it's a pollination issue.  Since its indoors, you don't have any bees or butterflies pollinating the flowers.  I'm new at this, so I may be way off base.  Honestly, I don't even know if tomatoes and peppers even need to be pollinated to go to fruit, but it seems likely.  You may want to look into learning how to manually pollinate them.  (Here's a link to an eHow article on it...

EDIT: I guess that's what your fan and you shaking them was for.  :D  Told you I didn't know anything.

I suspect there are a few issues in play, I can speak to the tomatoes, but my luck with peppers has been poor at best.  Mostly due to sunlight issues.  Like an idiot, I planted my peppers on the highest shelf, assuming that they would get better sun that way, but the tomatoes grew so tall, they were light deprived.  I've read here that if your nitrates are too high, the plants won't fruit, and suspect that is true.  Mine started flowering between 60 and 80 ppm.  I also suspect you're laking other micro/macro nutrients.  Cleaning up the plants as suggested earlier is a good start.  you may also want to "very gingerly" add fish fertilizer to the system along with some kelp and the other nutrients suggested on this forum.  Watch your numbers very closely as you do this.  Your system can get out of control very fast.  Your Ph is good for fruiting plants who tend to like Ph between 6.2 and 6.8.  Anything higher and the fruit retards and leafy greens tend to bolt.  How long are your days now, and what are your temps like?  They tend to like 10 hours sun per day and fruit in teh 70-80 temp range.  Although, I've seen many who successfully fruit between 60 and 70.  Hand polinating is a must, but its simple to do.  Hope this helps.  Keep us posted on your efforts.  btw, there are lots of cheap grow light options T5 and T8 dailight floresent seems to be cheapest, red and blue led are better (specifically red for fruiting plants).  Daylight LED should fully cover red and blue spectrum for you.

I don't understand why a system of less than one year does not have enough potassium for fruiting plants.

What happens in one year to an aquaponics system that gains potassium?

"Most people stick with non fruiting plants for the first year or so but I am not that patient LOL."

thanks for the posts,

I can't answer the potassium question--but be patient with me for a sec as I tell you what i've seen in my hydro system.   It might connect some dots...  But no promises. The key difference between aquaponics and hydroponics is in the hydro system, you have total control.  In aquaponics, you're at the mercy of your fish and your bacteria to get the job done.  And to date, i've not found any kind of meter to help measure what's happening in the aquaponics system...  So I tend to use my hydro system as a measuring stick.  In my hydro system, fruiting plants like a feed solution of about 850ppm, a ph of 6.2 or so and a water temp of about 70.  Leafy greens on the other hand...  600PPM of feed, 5.5 ph, and 60 or so water temp.  I use a balanced feed mix with all the macro and micro nutrients, that said...  The hydro system will drink copious amounts of the solution when its looking for something it needs.  Just as my tomatoes started to fruit, my system went from 25 gallons a week to almost 75 gallons per week and at best the fruit was stagnet.  Somewhere on youtub I read/watched something that said that fruiting plants need more potassium when they being the fruiting stage...  So I added potassium.  Feed consumption dropped back to normal and fruit started to appear, so for the next six weeks or so i continued the potassium regimine and then discontinued.  My beef steaks have produced a plathera of 1-3 pound tomatoes, my rutkers (sp) hundreds at 3/4 pound.  Thousands of grape and cherry tomatoes.  I've had fresh tomatoes in every meal, and both of my kids families and my two neighbors since mid july, and i've been canning about 4 pints of tomato sauce per week since then.  12 quarts of tomatoes = 4 pints of sauce.  My peppers, well they basically suck.  Did well with jalapeno's...

ONE HUGE WARNING...  In the aquaponics system you have to be very careful what you add.  I feel most comfortable using fish based or aquatic based fertilizers.  Strange as it may sound, ecological labs has a full line of organically certified fertilizers for aquaponics and hydro ponics, but I only use a limited number of their products.  Specifically photosynthesis plus, Nourish L and Niteout II.  The first two I use weekly and the latter monthly.  Niteout is intended to keep bacteria happy, while the other two keep the fish happy and help the plants be more efficient.  Since i've been using them, my fish have flourished.  But i'm still reluctant to add any fertilizer that is not aquatic based to the system...  That's just me though.

Thanks for the warning Robert and the info.  Lots to try to absorb.  I am also very jealous.  I want to tomatoes like you talked about (and green peppers).  So far, I dumped some good money into this and still not see a good crop.  Basil is growing like crazy and the fish seem to be doing very well.  I will look into the fertilizers you mentioned.  I forgot to mention I do add liquid seaweed.  I am trying to add about 1/3 of a cup each week.  The problem with the liquid seaweed is it turns the water opaque and I can't see the fish.  All my numbers are looking good.

Here is what I am trying (or will)

  1. I keep the temperature at 77-78.   I will think about lowering it.  I target this temperature since the is the best for bacteria.  Tilapia want 81-85 to really flourish.  So cold would not be good for them.
  2. I cut back on the tomatoes and pepper branches.
  3. I tried hand pollinating with q-tips on the peppers.
  4. Will continue to add liquid seaweed.
  5. I am going to bury orange peels in the growbeds for the potassium. 
  6. Need to check out the fertilizers.  I have plenty of Niteout II so it make sense to add a little each month.
  7. I am also will continue to dirty fish water right into the grow bed.


Thanks all for your comments.  Little frustrated but want the system to keep growing and start eating.


Good luck.  I will tell you my tomatoes are much slower in my aquapoinics system.  If I ever figure out green peppers, I'll certainly let you know.

Systems don't need to be a year old to support tomatoes or peppers, that's a common myth. In your situation, I would try to increase the feed amount. If you have zero nitrates, you may be starving the plants. As you feed more, the ph will begin to decrease which allows you to add pottasium and calcium as buffers into the system which will regulate your ph but increase the availability of these 2 much needed nutrients. I have hundreds of tomato plants thriving right now and they have been fruiting since a month after start up. Good luck!

I concur with Ryan. (Assuming other environmental conditions are on par)...Your zero nitrate reading can be looked at as perhaps an 'indicator' (somewhat at least) as to the status of other plant essential macro-elements. Assuming your using a well balanced feed...

For instance, Cargill's 24% protein feed contains about 3.2% nitrogen (N) and about 0.53% potassium (K). (On a dry weight basis)

So that's a pretty big difference already, and some plants are potassium hogs particularly around the fruit set and development stages of growth.

Of that 3.2% N, a tilapia fish will capture about 32.53% of that and convert it into bio-mass...the rest goes into the water stream as effluent...hopefully becoming mineralized and available to your plants at some point.

Of the 0.53% K about 7.16% is captured by the fish and converted into bio-mass. So K can often potentially be quite lacking. 

(These are mean averages which in reality differ according to what growth stages your fish are in)...

Increasing feed and using a potassium pH buffer sure seems like a good idea. (Along with that, there are also potassium mobilizing bacteria that could be added to help out with certain duties...though your on your own as to how you would go about adding them to your particular system 

Remember, fish feed and pH buffers are your main inputs on the plant end of things as well. (They're not JUST for the fish and bacteria).

thanks Vlad & Ryan.

I will try and feed more.  I have a hard time seeing what my fish eat in the aquaponics tank since I can't see them.  I have only been guessing based on 5 fish in a 48 gallon tank.  I will also try to add more potassium ph buffer more often.

I was in a similar situation a few months ago, added phosphorus  with white ash and a small piece of banana peel (potasium) to the growbeds also increased my fish feed till showing a trace of nitrates and the tomatoes and peppers fruited heavily.  my early girls split 60 per 100  and I decided they werent a good choice/pulled em out even though I outperformed 'dirt gardens who locally had lots of ripening issues this year,  i'll try one of the hydro happy breeds next year.

my peppers- new mex big jim and bell (lost tag)  are still producing slowly here at 43' N with system temps in mid 60's. cherry tomatoes started from seed oct 1 are now flowering

one difference we have is media  I used lava rock covered by granite pea gravel, for trace mineral I added a few quartz river rocks and put a couple chunks of basalt in fish tanks.  

 your photos look like you are about to be overun with fruit.

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