Weird white stuff on the bottom of my tank

ozeoze

Arachnopeon
Joined
Jun 6, 2025
Messages
2
I noticed this white stuff at the bottom of my tank when I was moving it. Can it be harmful to me or my millipedes? Mite eggs, mold? I have bumblebees, four adults and a lot of babies. Any help would be appreciated.
 

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chanda

Arachnoking
Old Timer
Joined
Jun 27, 2010
Messages
2,234
It is likely to be mold - unless you have sand mixed in with your substrate. I've found that when I mix sand with other substrate like coconut fiber, some of the sand settles to the bottom of the cage after time/repeated waterings.
 

HooahArmy

Arachnoknight
Joined
Jul 12, 2022
Messages
268
I'm going to say sand on this one. Fungi form web-like structures under the soil with their mycelium which honeslly do look like spiderwebs streaking about. The mycelium is usually white. I zoomed in on this picture and it looks like sand--sand just like the stuff I mix in my substrate and see at the base of my tanks myself!
 

CentiPete

Arachnopeon
Joined
Feb 3, 2020
Messages
26
Yup, sand that separates from the substrate over time. Nothing to worry about.
 

ozeoze

Arachnopeon
Joined
Jun 6, 2025
Messages
2
Yeah, I thought it looked more like sand or something but I'm not sure there is any in my substrate. I use premixed substrate of various kinds, one of them lists limestone as an ingredient, maybe that? I'll be checking if it spreads more though, in case it is mold. I haven't seen webbing or noticed any funky smells there. Thanks for all your responses.
 
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