We had a professional clean-out, poured bleach, poured salt water and plain salt down and around the drain (someone else's idea), stopped up the drain and flooded the shower then let the water rush through. No dice. They don't fly and don't even seem to do well with vertical surfaces. I've attached a picture. Any clues on what this is, why they won't go away despite our very strong hints, and what we can do? Thanks.