Talk about coincidence... just a couple of days ago I noticed something "weird" in my tank, some kind of invertebrate that lives in a tube and that seemed to put out a spider-like web and then reel it in later... I had never heard of that before, was really curious what it might be... and today I saw the article about vermetid snails in the magazine, that's exactly what I have! Now I'm hoping it's the kind that doesn't reproduce to plague-like quantities...
Nuno