Algae ?

[DougStanley]

I've noticed some dust looking substance on my decor, its on the driftwood, fake plants, etc.

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[rich311k]

If it is brown and dust like it is diatoms. A small organism that feeds on silicates. They are common in new tanks and will go away once the food source is depleted.

[DylanisHawttt]

+1 to the above.

All you can really do is wait it out. If you don't have any other algae outbreaks then keep doing what you're doing.

[DougStanley]

The reason I didn't suspect diatoms, this is not a new tank no new decor, substrate, or equipment was added. I know diatoms need silicate to eat and with no new things added I didn't see them being a problem. It was out of use for around a year maybe there problem.

Thanks