Small means small pond. A Kasko circulator is a special design and is not just a horizontally oriented water pump.
Your pictures are poor quality at best; too out of focus. It is like looking at your stuff through the bottom of a glass coke bottle. IMO others have it correct - doubtful it is duckweed. If you go the circulator route get the one from Kasko it is made to do what they are intended for. Now that you likely have FA a circulator may not be what you need since a circulator is better for duckweed than very coarse types of stringy FA.
