I emailed Pet Tech - they said:

Hello Jessica,

It is 100% safe and the residue is a food based mold release and will come off with a mild soap and water washing or it will dissipate over time. It has been used in amphibian enclosures in zoos to aquariums across the US and is popular with many frog enthusiasts.

Give it a good washing with a mild soap and it will be perfect.

Contact me with any other questions or concerns.

Best regards
...
So it should be sweet, yay!