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White mold on rocks?

Posted by SarahofLayton none (My Page) on
Wed, Sep 12, 12 at 11:39

I've made a few small closed terrariums, my most recent ones I used some 'river rocks' purchased at Hobby Lobby and I noticed last night that those rocks are growing, what appears to be, white mold. I took some out and washed them with a mild dish soap and put them back in. Was this the right move? Should I be worried? In both terrariums there are some of the same rocks at the very bottom beneath the soil for drainage, I'm worried that this mold is something that's going to kill my plants.
I've included an old post I found that just says to disturb the mold. Does anybody else have any experience.
Thanks for any advice!
(I'm new to the community and super excited about houseplants/ a fault even)

Here is a link that might be useful: closed terrariums post from 03

Follow-Up Postings:

RE: White mold on rocks?

Hi Sarah,

I don't think there is any problem with washing the mold off the rocks. I doubt the mold will kill your plants unless it gets so thick that is crawls up the stems and smothers them. Since you didn't display any photos I'm not sure what kind of mold you are talking about. If it grows again, a picture would be helpful.

What kind of setup do you have? I have a 10 gallon aquarium and I have kept the mold down by having a small computer fan come on four times a day for about 1/2 hour at a time. Also, it really isn't completely closed as the top is plexi-glass and that bends when humid and the corners have small gaps. This means the unit has to be watered occasionally. I think that also keeps the mold down.

It would be nice to see your setup. Can you display some photos? By the way, here is a link to my first terrarium.

My terrarium


RE: White mold on rocks?

Molds in closed terrs is pretty much unavoidable, IME. Sounds like some time of slime mold. Should be harmless to your plants and washing the stones off won't hurt anything. Many fungi love stagnant moist conditions. As Larry said, air circulation typically does wonders.

Happy planting!

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