I recently started a new hydroponic culture with an AeroGrow Aerogarden Harvest Slim. I put it in my house that doesn't have a good air circulation but bad neither; it's a standard room of ~40 square meter.

After about a week I was able to see the germination results, really small but visible. Suddenly, from day to night, checking my hydroponic I saw all the sponges and pods totally covered by mold.

The days before I checked the pH and it was correct, nutrients too. What could the problem be in that situation?

I thrown it all away and I would really like to try again but I'm not able to understand the problem. How can I investigat about it?

  • Have you thrown them out yet? If not have you thought about a weak solution of H2O2. It would kill the mold but not hurt the plants. I'm not sure the exact strength that is safe on plants. I looked it up and found this for killing powdery mildew on plants. I know that is completely different, but it gives you the ratio of H202 to water that is safe; hunker.com/13427143/…
    – GardenGems
    Nov 6, 2019 at 18:35
  • Yes I thrown them away and I cleaned it all. It was an "experiment" for me and I made for sure a few mistakes so I preferred to do that and I will try another time in a few days. I think I've to focuse a little more on the germination phase then the enviroment should be ok. Anyway thanks. Nov 7, 2019 at 10:04
  • First we need a positive id on the "mold" - do you mean mold or algae? Mold will need some organic material to parasitize, whereas algae will grow in a rich wet oxygenated environment without anything organic as host. Nov 8, 2019 at 11:56

1 Answer 1


The problem is most likely a poorly sterilized environment. You created a situation where almost anything you planted would thrive. Unfortunately for you mold is much higher up on the evolutionary scale than the plants you wanted to grow are. In fact, in terms of evolution, mold is second to none. Therefore, I would suggest you thoroughly sterilize the environment with rubbing alcohol prior to planting anything on the next go around.

However, it could also be that there is mold spores in the air. If that is the case it's going to be hard to grow anything that isn't growing in soil. If you try again and again you fail despite your attempts at thoroughly sterilizing the environment than I would suggest you call in a professional to do some testing for mold.

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