It might take a long time to settle if you hadn't wash the eco first ...... My first choice is to drain out all the water (with the fine dust), then refill carefully to not kick up any more dust. (The classic way is to put a big clean plate on top of your substrate & carefully pour in new water.) Alternatively, you can try filtering out the dust. A Magnum with a water polishing cartridge will take care of that in a couple hour, although you might have to rinse out the filter a few times if it clogs.
80 gal FW with 30 gal DIY wet/dry/sump.
9 fancy golds, 1 hillstream loaches, 1 rubber-lip pleco (C. thomasi), 3 SAEs, small school of white cloud minnows, planted.