Week 2: Plagued By Algae and Mold

Marbles Week 2 Bonchi Seedling

At the end of last week’s post I mentioned how I had noticed some algae growing on my rock wool. This week saw the growth of algae, and mold, go rampant.

Mold and Algae Growing on Rock Wool
Mold and Algae Growing on Rock Wool

Whilst I have dealt with algae before, never have I had it this bad! Something has changed within my growing environment; I suspect that as the weather outside turns warmer, the plant room now reaches an overall warmer temperature. This could be a contributing factor.

Unfortunately it seems that some of my seeds did not germinate, and most likely will not. Chances are I will discard the algae infected rock wool cubes and do a big clean.

Another means of combatting mold and algae is to increase airflow. Currently I have clear caps on the cups to increase moisture levels (seeds germinate better in high humidity). I may begin to remove the caps overnight so that they have time to dry out and get airflow, and return the caps during the day when the lights are lit so not to dry out the seedlings too much.

Seedling Dying. Too much algae?
Seedling Dying. Too much algae?

So far only one of my seedlings seem to be loosing the battle of life. It’s not too uncommon for seedlings to not survive, so I can’t be certain whether this is the cause of algae or not (it most likely is however). Initially the cotyledon leaves started to wilt, but it started to grow its first true leaves. However you can see that even those have begun to wilt as well.

Marbles Week 2 Bonchi Chilli Pepper Seedling
Marbles Week 2 Bonchi Chilli Pepper Seedling

It’s not all bad news. Some of the seedlings are growing quite well despite the algae. The Marbles variety seedling has grown its first true leaves.

I have a total of 9 seedlings growing their first set of leaves. There are 3 seedlings that appear sick (like above). And finally there are 3 seeds that never sprouted.

Honestly if 9 of the seedlings survive and grow into trees, I will be happy.

2 thoughts on “Week 2: Plagued By Algae and Mold”

    1. I took off the lids, and on some the algae seemed to dry out. However on other rock wools they continued to grow slimy and green.

      Since then I have added a few drops of diluted Hydrogen Peroxide (H202) onto the Rockwool, which interestingly fizzed! I have also added some food grade diatomaceous earth powder on top which can discourage gnat flies and algae. I’ll update soon to see if it worked!

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