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I replaced my depleted liquid Aerogarden fertilizer with 3-3-2 AgroThrive Organic General Purpose Liquid Fertilizer. I maintained the same feeding regimen: two capfuls every two weeks. My herbs are not growing, and are in fact wilting and turning purple. Another worrying development is that the water has turned foamy, and coated the grow sponges in a mild slime. Could I revive my herbs by changing my regimen, or do I need a different fertilizer?

Compare the unhealthy herb in the foreground with the seedling in the background

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The AgroThrive website doesn't list a 3-3-5 product called "AgroThrive All Purpose Organic Liquid Fertilizer." They have a 3-3-2 product called "AgroThrive Organic Fertilizer - General Purpose" and a 3-3-5 product called "AgroThrive Organic Fertilizer - Fruit & Flower." Both products have the same instructions for use in hydroponics:

Dilution & Instructions For Use: Introduce AgroThrive products gradually to give microbes a chance to establish growth on the support medium. Add soil, rocks, coco coir, or another support medium to give the roots somewhere to go besides floating in water. Then start with less than 1% AgroThrive product and gradually increase the concentration every couple of weeks until you notice phytotoxicity. Then, return to highest safe product dilution.

Tips: Hydroponic systems skip the soil, substitute different materials to support the roots, and grow crops in nutrient-rich water. Hydroponics does not provide enough time for microbes to digest higher molecular weight nutrients needed by plants. A medium is needed to harbor microbes which will prepare the organic fertilizer for plant use. (source)

If you followed the instructions, then it sounds like you've reached the "until you notice phytotoxicity" stage, which means it's time to "return to highest safe product dilution."

It sounds like you may have introduced the product all at once, which is not the recommended way to use this product. If that's the case, you may want to start by reducing the application rate, and consider contacting AgroThrive customer support for further advice.

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  • Indeed, it is 3-3-2; I had copied a typo from the Amazon listing. In practical terms how should I implement this needed "medium" to harbor microbes? Are my herbs resuscitable?
    – Emre
    Commented Apr 22, 2021 at 18:52
  • Your herbs look pretty rough, but the only way to know if they'll survive is to dial back the fertilizer and see if they recover. If you need more detail than "add soil, rocks, cococoir or another support medium," you might need to post another question for that. Although it might also be worth asking customer support if your current growing medium is adequate. There really wasn't enough detail on their website for me to figure that out.
    – csk
    Commented Apr 23, 2021 at 0:51
  • Adding soil to a (hydroponic) Aerogarden seems inimical to me. Is anybody else doing this? On your advice, I did ask AgroThrive, and am awaiting a response.
    – Emre
    Commented Apr 23, 2021 at 0:56
  • If they get back to you with useful information, you can post it as an answer to your own question, and it may be helpful to other people. If you're not sure how to add a substrate to your hydroponic system, it might be worth posting a separate question about that, including details and photos of your system. Some hydroponics systems use a substrate to provide support for the roots and others don't, so it may depend on how your system is set up.
    – csk
    Commented Apr 23, 2021 at 1:09
  • I use grow sponges as a substrate, and as I mentioned in the post, they are now partially coated in sludge.
    – Emre
    Commented Apr 23, 2021 at 1:25

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