[Priscilla]

I was just looking at my tank as usual but today I noticed this smokey looking thing on the cave. Does anyone know what is this?

8390f9eacda5390c1fa75af3cd41eaa5.jpg (87.09 KiB) Viewed 8565 times

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[opae ula related]

It's GhostBusters!!

[opae ula related]

Joking aside, dont know what it is but I would personally remove it.

[odin]

I've had this in my newly setup fresh water tanks when i've added wood or similar, i cant be sure if its the same stuff but it wasn't harmful to the fish or shrimp. I would probably just remove the cave and scrub it in some fresh RO/distilled water or what ever you use just to be on the safe side just in case.