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I have a new aquaponics setup and need some help with a few problems.

Setup

  • CHIFT PIST  
  • Sump pumps to grow beds, grow beds flow to fish tanks, fish tanks flow to sump
  • 2 - 175 gallon IBC fish tanks with SLO and approx. 60 1" - 4" koi in each tank
  • 175 gallon IBC sump tank
  • 3 IBC grow beds with Utelite media planted with tomatoes, cucumbers, eggplants, peppers, lettuce, and spinach
  • PH tends to stabilize at 8.0 - 8.2.  Use Muriatic Acid to try to bring it down.
  • Added Maxicrop liquid seawead (60 ml) and postasium sulfate 0-0-50 (0.3 ounce) about two weeks ago.
  • The water temp stays between 70 - 72 f (heated)
  • 70 LPM Active Aqua 60 watt air pump with 4 medium stones in each fish tank
  • The air temp ranges between 55 F and 100 F.  It has been between 55 F and 73 F for the last 5 days. 
  • Planted and added fish on 4/7/2016
  • Water test on 4/28/2016: PH 8.0, Ammonia 0.0, Nitrite 0.0, Nitrate 40-80
  • All inside a 10' x 12' greenhouse

Problem:

My tomato leaves are curling and my cucumber leaves are yellowing and dying on the edges.  Also, the shishito Peppers are curling a bit.  Lastly, some of the leaves on the eggplants are lighter green.  Here are some pictures:

Tomato

Cucumber

 
Pepper

 

Eggplant

The color of the eggplant leads me to believe I need to add iron.  I have EDDHA Iron Chelate 6.0%, but am not sure how much to add, or if that is even the problem.  As mentioned above, I also have Maxicrop Liquid Seaweed and Potassium Sulfate 0-0-50 at hand.

Any suggestions on what to do would be greatly appreciated.

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Craig, 

The first thing that sticks out to me is that your ph is too high, especially for your tomatoes. Tomatoes like a ph of 6.0 to 6.8, and this is essential for the proper uptake of nutrients. The second thing I will mention is the age of your system. From what I've heard and seen, it takes at least 6 months for a system to settle in and work out all the kinks. My system started producing ok after about 3 months, but didn't really get going till the next year. 

With that said, I have added iron, egg shells, banana peels and rock phosphate to my system to try and balance nutrients and still I have had problems with some of my tomatoes curling and dying and my cucumbers not doing well in my system (which is very much like yours). One thing I may try soon is to lower my water level and allow more "dry zone" for the tomato roots. I'm not sure this will work though and am hesitant to change this as it will effect the rest of the plants (kohlrabi, lettuce, sage...)  which seem to be doing fine. 

(my 2 cents)

It does look like your pH is too high and Nitrates are minimal. Try more food for the fish until you see ammonia rising. My system rarely sees 0 ammonia. That should raise your nitrates and nutrients in general. I see that you're pumping from your sump to your GBs. Most systems go from the FT to GBs sometimes with a swirl or radial filter between to pick up the solids. The beds drain to the sump and the pump is in the sump. What will probably happen is your solids will settle in your sump and eventually cause issues.

Thanks for the input.  That makes sense.  I am working to bring the pH down using muriatic acid.  Also, I have read that it should come down naturally as the system matures.

Regarding the buildup of solids in the sump, I have seen that.  I have been sweeping them towards the pump every few days to keep it clean.  I don't know that I have an easy way to modify this without a major overhaul.  One simple solution, however, would be to add a grow box or two below the level of the existing fish tanks.  The flow would then go sump=>grow beds 1,2&3, then grow beds 1,2&3=> fish tanks 1&2, then fish tanks 1&2=> grow beds 4&5, then grow beds 4&5 to sump.  This would filter out the solids into grow beds 4&5, but wouldn't put much solids into grow beds 1,2&3.  I don't know if that is important.  

I have always planned on adding two more grow beds, as I have the space in the greenhouse.  I just don't know if that will be too much growbed for my fish tanks.

I think you would have to go a long way to have too many grow beds as you can increase feed rate to the fish to increase plant nutrients. As for your sump setup, as long as the water level in the fish tank is higher than the grow beds and the sump is the lowest point in the system changing the plumbing is all you need to do. I know it's a pain but I've done major modifications on my system 3 times and it's worth it in the end.

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