Backyard Aquaponics
A place to discuss aquaponics

Hi Folks,

We fired up our system October 2018, it is located in a green house that gets no colder than 55 F. The plants tomatoes, peas, green beans, radishes that we planted at that time really took off. Lettuce in two DWR did well also. We are currently have the 2 DWR and 6 grow beds in production. Then our 2 tomato plants started looking odd. On doing some research on this site I think that we do not have enough fish in our system to provide the right food mix for the tomato plants.

We have a 1,400 gallon fish tank and a sump under the grow beds that holds around 300 gallons. We have 55 hybrid blue gill that are about 4-5" long. I wanted to start slow and was planning on adding 50 crappie to the mix this spring.

Iron 2.52 PH 6.7 AM., Nitrates and Nitrites are fine.

1.) Am I correct that I need more fish?

2.) Can I add tilapia to the blue gill, crappie mix?

Thanks in advance for your help.

Are you getting some particular deficiency in the tomato plants? Got a picture? What's the volume of your growbeds?

Unless you can find a rare source of already pellet trained crappie they will nearly all die most likely, unless you plan on feeding them a live diet that is

The grow beds are 50 gallon, I'll get a picture of the tomato plants tonight.

The plants went for perfectly to this in about 2 weeks.

Your stocking density does sound low to me. That looks a lot like potassium deficiency though, and this problem would not be caused by a low stocking density since potassium typically has to be supplemented. Perhaps try dosing up with potassium and seeing if that helps? I use liquid seaweed extract, but there are other potassium sources which are suitable for aquaponics.

If that doesn't work, it may be magnesium, in which case I would add epsom salts. The deficiencies present similarly in tomatoes.

Hey ONG2, I see this issue was a couple of months ago and you've may have sorted it by now, but for what it's worth I would suggest that you have either a Magnesium deficiency or a bacterial infection. It's not a Potassium issue.

Looking at the pics, my money would be on Magnesium, in which case adding additional Potassium to the system could exacerbate the problem. Try 1x heaped teaspoon of Epsom salts per 1000L of water, or you could use Dolomite lime at 1x heaped teaspoon per 1000L, this will also help maintain an buffer the system pH. You can also just sprinkle the Dolomite in the gravel around the root zone of the affected plants.

What is your Nitrate level?... In most situations this gives a good indication if you have sufficient fish numbers in ratio to plants in the system... Except if you are removing fish waste solids from the system, not collecting and treating those solids to reclaim nutrients locked up within them, and then returning those nutrients back to the system, in which case you could have high Nitrates in ratio to other essential mineral elements.