Aha so this is why it sinks in my pond maybe? We have cool, cloudy days a lot here! Also I read that any pull from a pump or falls giving the water the slightest amount of movement will suck it down under also. It does not sink in my non-water-moving tubs around the yard.
Taken from the net:
Anacharis- wild grows all over North America (including Canada and Iowa) and South America. You'll probably never see it in your aquarium, but anacharis moves up and down in the water depending upon water temperature and light. In your water garden or tank you may see tiny bubbles of oxygen escaping from your anacharis leaves. In the wild, this product of photosynthesis causes anacharis-wild to float, unless well rooted, on warm, sunny days and sink on cool, cloudy days. As an add plus, Anacharis eats fish wastes -- carbon dioxide, nitrogenous, and phosphate wastes. You can do fewer water changes, however, fewer water changes also slow the growth of anacharis. Although anacharis eventually grows roots, it takes in most of its food directly thru its leaves. This makes anacharis an excellent algae competitor. Anarchis-wild will do its best to starve out algae which will help keep ypur water cleaner! Pond owners use anacharis as an aerating plant as well as an algae competitor.
