I wouldn't think that a small amount would be harmful, but I'd definately want to avoid his ingesting it. You could put a flat piece of, say, clear plexiglass on the floor of the tank before feeding, and feed on top of that. or use an overturned coffee saucer, plant-pot tray, or even a piece of astroturf for the same purpose. I personally use an overturned water bowl, and it works great.

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And humans are supposed to be the world's most intelligent, civilized, and refined species, eh? Have you ever been in a crowded discount store?