The one that was originally on the Purigen packet was in the filter compartment and the filter intake is near the heater. At that time, it might have been the warmest place.
Picture a 20L. The filter is on a short side. The powerhead and heater are also on that same short side. After I photographed the bag, I clipped it on the other short side. So, that ought to be much cooler. But the larger one (that has tentacles showing) made its way all the way across to join up with the foot on the bag.
But in between, I did add a small heater into the filter, and the wanderer may have been seeking cooler at that point.
Dawn moved the Purigen bag to mid-tank, under the light.
It's a mystery, especially how the foot got into the filter, given that the intake is usually pretty well covered up by chaeto.
(Yes, this is like the sloppiest tank ever.)