aquarium parasites

Question
Hi Karen: I have 10 tanks ranging in size from 1-20 gallons.  I do not generally lose fish and therefore have not added new fish to my tanks in the last year. I  had tanks with snails, but I have removed the snails from  my tanks and put them in a fish bowl because they would overpopulate in the tanks and climb above the water level and die attached to the glass.  They rarely seemed to die in the tanks and I didn't find many shells in the gravel at cleaning.  The snails in the fish bowl seem to have one long white string attached to them?  Is this some sort parasite?  If it is, is it dangerous to fish or humans?  Also, for the past 6 months at cleaning I have minute black specs that swim around in the water (just one of the tanks that had a lot of snails).  I thought they might be free swimming stage of snails, but no snails have developed.  Are they some sort of parasite? Multiple water changes and severe (75%) water changes do not seem to reduce them.  I have had guppies and mollies and bettas, plecostamus and catfish in with the snails and they neither eat black specks or seem to get sick.  Thanks.  BTW, I have read other answers by you and am impressed with your knowledge.

Answer
Hi C, (Thank you for your wonderful compliments!)

The long white string is most likely waste from the snail. Perhaps from not getting enough to eat or stress. But they will likely recover fine.

I'm not sure what the black specs may be. There are many crustaceans and "bugs" that can get into our tanks and bowls. They are all mostly harmless scavengers that feed on excess waste and organic matter in the tank. I can bet if you removed their food source (excess waste matter) continually and persistently, they'd eventually die off. Try using your gravel vacuum to siphon them up as much as possible.

I hope this helps and best of luck!
Karen~