Backyard Aquaponics
A place to discuss aquaponics

Hello everyone!

We are a couple from Greece and started our small IBC aquaponics system about 1,5 month ago. My husband did most of the original research and now I'm following too. We have two children, a daughter 23 months-old and a son 8 months-old, so my schedule is usually full but I manage to take care of our system once or twice a day.

We have an IBC unit cut in two uneven pieces, where one piece is used as a 30cm-depth grow bed and the other part is our fish tank (appr. 800lt). We used pumice for the grow bed and started cycling the system with no fish, by gradually adding some ammonia and testing the water everyday. It took some weeks to start having nitrites and nitrates readings (will post the test results later), but we were impatient and added the plants to see them growing (2 tomatoes, 4 cucumbers, 1 squash, 1 eggplant, 1 green cupsicum, 24 lettuce plants). Days have passed and both ammonia and nitrites went to zero and we only had nitrate readings. That was the day that we added 11 goldfish (it is extremely hard to find Nile Tilapia in Greece).

The plants' growth was amazing the first weeks, but the last 2 weeks something has happened and the plants gradually started to look sick. Although they gained height and looked healthy, suddenly their leaves started to turn yellow and rotting (attaching photos and a video of the system before the plants).

Current readings:
pH: 8,2 (constant since day 1)
Nitrates: 10ppm
Nitrite: 0,01-0,025ppm
Ammonia: 0ppm

Unfortunately we already lost two fish and the plants seem to die. Any advice in general would be very appreciated.

Thank you in advance!!
Cheers!

https://www.youtube.com/watch?v=q-6XxbMjVKM

Welcome to the forum Rotty

Sounds like your system has cycled. It looks like there are several things going on and I'll go from the highest picture in your post to the lowest.

Picture 1 - Probably Potassium or Magnesium deficiency (although I'm not sure about this).

Picture 2 - Looks like some rot going on and possibly leaf miner damage. I'd pull all the leaves but the top 2 and dispose of them in the garbage, not the compost. You might want to pull the plant and check the roots - if they are rotted then just throw the plant.

Picture 3 - Looks like what happens when water splashes on the leaves and the tissue collapses. Try not to splash on the leaves or stop this if you can. I think mold is what actually causes the damage but the water just gives it a chance to do this.

Picture 4 - Same as 1

Picture 5 - Same as number 1

Mobile and Immobile Nutrients -
Mobile Nutrients - Deficiencies show on old growth first
Nitrogen, Phosphorus, Potassium, Molybdenum, Magnesium and Zinc

Immobile Nutrients - Deficiencies show on new growth first
Iron, Copper, Manganese, Chlorine, Cobalt, Boron, Calcium, Sulfur

You can see in the pictures the top growth is green and that indicates this is being caused by a mobile nutrient (it can move into the new leaves from the old).

Check for spider mites on the plant in the first pic - the spots make me think this is a possibility. Assuming it's not mites, on the plants with the deficiency I'd do the following on all the plants but a few days apart -

1. Spray with Epsom salts (Magnesium Sulfate) - A teaspoon of Epsom salts per 1000L or a smaller foliar dose 375g to 20 litres - (from the product label Faulding Epsom Salts someone posted on BYAP).

2. Spray with Potassium bicarbonate (probably mixed at 15gm/3.8L or 1Tbsp/Gallon of water) OR Maxicrop plus iron (For foliar feeding 1 Oz per gallon or about 30mls per 3.8 L then spray directly on plants.)

Getting the deficiency to go away make take several applications about 1 week apart. Once the deficiencies have vanished stop applying these.

I'm not sure of the Magnesium Sulfate or Potassium bicarbonate dosages so if you notice any problems that you think are related to the spray (like the chemical burn that over fertilized plants get) then stop.

Hope this helps.

Found out on the Magnesium that you should not apply it on bright sunny days or over apply it because it can cause leaf scorch - so use caution.

Thanks a lot for the response really appreciate it
Already got the Epsom salt but considering the Potassium supplement I want ask is it "ok" to use Potassium bicarbonate since pH is already high (8.2)? Wouldnt it be better to use potassium sulphate or even pure pottasium?

Have a bad start .. although mater cycled perfectly two weeks after planting the plants are having serious problems as u can see (n today r even worse) and out of 11 goldfish Im down to 7.