Duckweed devourers

My small pond was more or less covered in duckweed with pondweed growing through it. There was very little free water. Within a matter of days the pondweed has disappeared except under the shade of surrounding plants that flop over the water. This seemed to me quite amazing, knowing what a devil it is to get rid of manually. I had noticed a few little creatures moving slowly across the surface that appeared to be caddis larvae with duckweed as their casing! Today I did a dedicated sit by the pond to watch, as now the pond weed is being eaten - big circular areas missing from leaves, some eaten altogether. As I sat I saw plenty of these surface feeding creatures eating the leaves. They seemed to also have a long tube (maybe tubes?) that occasionally came out of their head end. This pond is about ten years old and I've never had anything like this before. I reckon it will be stripped of pondweed within days at this rate.